Across
Stop key piercing skin (7)
One of those on the board in 'otel on street (7)
12a
Temple say, where church dignitary originally involved in criminal trials (5,4)
See 17 Down
Where heaps could be made flabby? (3,2,5)
See 9
Turn up for yoga class, did you say? Boo and hiss! (12)
Like some old houses where two little boys live with socialist behind hospital (4-8)
I haven't cracked this one yet — but Fifteensquared have:
[ ALF,TIM(two little/shortened names for boys) + BE(to live/exist) plus ( with ) RED(a communist or socialist) ] ] placed after ( behind ) H(abbrev. for “hospital”).
Titaness back on the radio? (4)
Playful crime fools jerks (10)
Those increasing pace of journey narrated story with twists (4,5)
Defeat finally complete after reversal, lose it (5)
I haven't cracked this one yet — but Fifteensquared have:
Reversal of ( … after reversal ) [ last letter of ( … finally ) “ Defeat ” + PURE(complete/involving nothing else, as in “a complete waste of space”) ].
Country game on river recalled (7)
I haven't cracked this one yet — but Fifteensquared have:
Reversal of ( … recalled ) [ GIN(a form of the card game, rummy) placed after ( on ) AIRE(a river in Yorkshire, England) ].
Naked dean back from Japan, say (7)
I haven't cracked this one yet — but Fifteensquared have:
“ dean ” minus its 1st and last letters ( Naked … ) + STERN(the back/rear, of a ship, say).
Down
Priest runs after page 3, for example (6)
Hot under the collar, collared and cuffed? (6)
I haven't cracked this one yet — but Fifteensquared have:
SHIRT(a garment with a collar/collared and cuffs/cuffed) -Y(suffix indicating “has the characteristic of”, as in “storm/stormy”).
Suffering if in need, it's endless (10)
I haven't cracked this one yet — but Fifteensquared have:
Anagram of ( Suffering ) [ IF IN NEED + “ it’s ” minus its last letter ( endless ) ].
Huddersfield initially at bottom of division - how far down? (5)
I haven't cracked this one yet — but Fifteensquared have:
1st letter of ( … initially ) “ Huddersfield ” placed below ( at bottom of , in a down clue) DEPT(abbrev. for “department”, a division of an organisation).
Explosive ingredient key in spirit, head of course blowing off (9)
I haven't cracked this one yet — but Fifteensquared have:
ALT(abbrev. for “alternate”, another key on your computer keyboard) contained in ( in ) “spectre”(a spirit/a ghost) minus ( … blowing off ) 1st letter of ( head of ) “ course “.
Island, 1/63,360 miles (4)
Feline and little piggies guzzling a fruit of the vine (8)
I haven't cracked this one yet — but Fifteensquared have:
[ TOM(a male feline/cat) plus ( and ) TOES(called “little piggies” by young children) ] containing ( guzzling ) A .
Relative instructed to cover a baked food (3,5)
I haven't cracked this one yet — but Fifteensquared have:
NAN(familiar term of address for one’s relative, viz. grandmother) + BRED(instructed/trained and taught to behave in a particular way) containing ( to cover ) A .
Where bishop might have to move quickly, sermons about five hundred seconds (5,5)
I haven't cracked this one yet — but Fifteensquared have:
[ SPEECHES(lectures/sermons) containing ( about ) D(Roman numeral for five hundred) ] + S(abbrev. for “seconds” in time notation).
Notes in old currency collected by Paul and mum (9)
I haven't cracked this one yet — but Fifteensquared have:
[ O(abbrev. for “old”) RAND(basic currency unit of South Africa) ] contained in ( collected by ) [ ME(Paul, this crossword’s setter, using the self-referential pronoun) + MA(a familiar term of address for one’s mother/mum).
20d
Dance bands on with the mostly funny old player (8,6)
10a
Hump: cop off in the arms of Morpheus? (8,9)
Amount of space in book (6)
See 16
Thread is line in middle of bulletin (5)
I haven't cracked this one yet — but Fifteensquared have:
[ IS + L(abbrev. for “line”) ] contained in ( in ) middle 2 letters of ( middle of ) “ bulletin “.
Capsizing in warfare, weakened vessel (4)
Type letters or click words in the clue