Across
Develop complex (9)
I haven't cracked this one yet — but Fifteensquared have:
Double defn: 1st: To add more detail to, say, a theory, policy, or basic story line; and 2nd: Involving many complicated parts and details.
Dunce Tees had nothing invested in it (5)
I haven't cracked this one yet — but Fifteensquared have:
I’D(Tees’d/Tees had, with the setter using the self-referential pronoun) + [ O(letter representing 0/nothing) contained in ( invested in ) ] IT .
Red 6 held back in trade centre as 9 is in catalogue (7-8)
I haven't cracked this one yet — but Fifteensquared have:
Reversal of ( … held back ) SIX(6) contained in ( in ) MART(trade centre/market) + reversal of ( as … is /is held back like 6 in the first half of the clue) NINE(9) contained in ( in ) LIST(a catalogue/a register of items).
Killer in wood, wife smiled devilishly in repose (5,3,7)
I haven't cracked this one yet — but Fifteensquared have:
DUTCH(one’s wife, especially among Cockneys, from “duchess”) + [ anagram of ( … devilishly ) SMILED contained in ( in ) EASE(repose/in a state of comfort) ].
Aircraft enclosure's energy supplied with sodium battery (7)
I haven't cracked this one yet — but Fifteensquared have:
E(abbrev. for “energy” in physics) placed after ( supplied with ) [ NA(symbol for the chemical element, sodium) + CELL(a battery/a device for converting chemical energy into electricity).
Nuclear installation on river unstable at core (7)
I haven't cracked this one yet — but Fifteensquared have:
Reversal of (abbrev. for “river”) + anagram of ( unstable ) AT CORE .
Not all there spreading nepotism among subordinate officers (3,6,6)
I haven't cracked this one yet — but Fifteensquared have:
Anagram of ( spreading ) NEPOTISM contained in ( among ) NON-COMS(short for non-commissioned officers, subordinate to commissioned officers).
Unorthodox ideas after blood found in Icelandic parliament (7,8)
I haven't cracked this one yet — but Fifteensquared have:
LATER(after, in time) + KIN(blood/familial relations) contained in ( found in ) ALTHING(the Icelandic parliament).
Cat wants mouse's heart brought in as soon as (5)
I haven't cracked this one yet — but Fifteensquared have:
Middle letter of ( …’s heart ) “ mouse ” contained in ( brought in ) ONCE(as soon as, as in “once you have done the first step, go on to …”).
Clear directions when entering old address (9)
I haven't cracked this one yet — but Fifteensquared have:
N,E(abbrev. for “north” and “east”, two directions) contained in ( when entering ) [ EX-(prefix signifying “old”/former) + ORATE(to address/to give a speech) ].
Down
Rook on wet earth trapped by head islander (8)
I haven't cracked this one yet — but Fifteensquared have:
[ R(abbrev. for “rook” in chess notation) placed above ( on , in a down clue) MUD(wet earth/a soft sticky mixture of earth and water) ] contained in ( trapped by ) BEAN(informal term for one’s head).
Polly run over, which stops involvement (6)
I haven't cracked this one yet — but Fifteensquared have:
[ R(abbrev. for “run” in cricket scores) + O(abbrev. for “over”, again in cricket scores) ] contained in ( which stops ) PART(involvement/contribution to an action or situation).
Reduced ambition to join one native group (4)
I haven't cracked this one yet — but Fifteensquared have:
“hope”(ambition/aspiration) minus its last letter ( Reduced … ) plus ( to join ) I(Roman numeral for “one”).
Transport ecstasy left for political alliance (6)
Footballer put off allows goal in (8)
Sometimes dotty characters supporting feminine state? (4)
I haven't cracked this one yet — but Fifteensquared have:
I,J,I(characters/letters having dots/dotty sometimes, viz. when written in lower case) placed below ( supporting , in a down clue) F(abbrev. for “feminine”).
Limit broken: industrious worker becoming aggressive (8)
I haven't cracked this one yet — but Fifteensquared have:
Anagram of ( … broken ) LIMIT + ANT(an industrious worker in an ant-hill).
United in mess, bust possibly (6)
Tragedy to be denied sacred books — are you listening? (5)
Underworld Society brought up ghost (5)
I haven't cracked this one yet — but Fifteensquared have:
HADES(the underworld/the underground abode of the dead in Greek theology) with “s”(abbrev. for “Society”) moved to the top of the word ( brought up , in a down clue).
Insincere talk about on street? It's true! (8)
I haven't cracked this one yet — but Fifteensquared have:
CANT(insincere/hypocritical talk) containing ( about ) [ ON + ST(abbrev. for “street”) ].
Tree forced flat to sprawl among scattered pears (8)
I haven't cracked this one yet — but Fifteensquared have:
LIE(to sprawl/to lie with arms and legs outstretched) contained in ( among ) anagram of ( scattered ) PEARS .
Reconciled where gender is not fixed? (8)
Our highest military man with grip on opponent? (6)
I haven't cracked this one yet — but Fifteensquared have:
Double defn: 1st: Cryptically, refering to the statue of Admiral Nelson standing on his monumental Column high above Trafalgar Square, London, and presumably above any statue of an English military man; and 2nd: … in the wrestling ring.
Southern fan guards principal in Harrow train (6)
I haven't cracked this one yet — but Fifteensquared have:
S(abbrev. for “southern”) + COOL(to fan/to create a current of air that will effect cooling) containing ( guards ) 1st letter of ( principal in ) “ Harrow “.
Island where Brown consumes excellent whiskey (6)
I haven't cracked this one yet — but Fifteensquared have:
TAN(brown colour) containing ( consumes ) [ AI(A1/of an excellent grade, with the Roman numeral substitution) + W(letter represented by “whiskey” in the phonetic alphabet) ].
Impolite daughter taken down felt remorse (4)
I haven't cracked this one yet — but Fifteensquared have:
RUDE(impolite) with “d”(abbrev. for “daughter”) moved to the end of the word ( taken down , in a down clue).
Swede regularly entered Portugal (4)
I haven't cracked this one yet — but Fifteensquared have:
2nd, 4th and 6th letters of ( regularly ) “ entered ” + P(International Vehicle Registration code for Portugal).
Type letters or click words in the clue