Across
State of Britain boosted with a victory song (7)
Chap needs a support of course – a ‘cow’ mainly! (7)
I haven't cracked this one yet — but Fifteensquared have:
definition: a manatee may be called a ‘sea cow’, with “mainly” as in ‘the main’=the sea MAN=”Chap” + A TEE [for a golf ball]=”A support of a [golf] course”
Stew of sheep’s head and flounder (7)
I haven't cracked this one yet — but Fifteensquared have:
head letter of S-[heep] + WELTER=to be in turmoil=”flounder”
Career Oscar? Not finalised – go berserk! (3,4)
Silly novel ‘Four’ is at heart only half a book (9)
I haven't cracked this one yet — but Fifteensquared have:
anagram/”novel” of (Four is)*, with VOL-[ume]=”half a book” inside/”at heart”
Heading off for relative release (5)
I haven't cracked this one yet — but Fifteensquared have:
[a]-UNTIE=”relative” with head letter taken off
Dash off genuine short (5)
Don’t be so appreciative – it’s unrewarding (9)
No star fouled a sporting opponent (3,6)
I haven't cracked this one yet — but Fifteensquared have:
BIT as in ‘to bite’ – to bite another player might be to ‘foul a sporting opponent’
Supplier, in quotes, ‘Corporation’ (5)
Apple disheartened by this device? (5)
New, albeit fancy, consumers’ drink (5,4)
Musical bag, lock container (7)
Hill in position above city (7)
South, if not cloud-covered (7)
Supermarket workers disposing of small notebooks (7)
Down
Retiring party, almost packed (7)
Contend with annexe inspection (7)
Secret royal houses in a past style (5)
Rarity who is excited to be allowed to fly (9)
I haven't cracked this one yet — but Fifteensquared have:
anagram/”excited” of (Rarity who)*
Anti-capitalist’s sound old currency (5)
I haven't cracked this one yet — but Fifteensquared have:
definition refers to e.g. German Deutsche Mark currency, used before the euro sounds like ‘Marx’, as in Karl Marx (“Anti-capitalist”)
College intrudes on UK tenant developing Massachusetts resort (9)
I haven't cracked this one yet — but Fifteensquared have:
C (College) inserted into an anagram/”developing” of (UK tenant)*
What I have here: yarn – not a thing to prick you (7)
I haven't cracked this one yet — but Fifteensquared have:
THIS=”What I have here” + T-[ a ]-LE=”yarn” minus the ‘ a ‘ i.e. “not a “
Aims to keep the French Sabbath going for ever (7)
I haven't cracked this one yet — but Fifteensquared have:
ENDS=”Aims”, around (“to keep”) LE=”the [in] French”, plus S (Sabbath)
Dream about cry of encouragement abroad leading to resistance (9)
Short book Croatia translated, about performing as a gymnast (9)
I haven't cracked this one yet — but Fifteensquared have:
anagram/”translated” of (B Croatia)*, with B=”Short book” plus C (circa, “about”)
‘God’ misspelt as such, after carriage return (7)
I haven't cracked this one yet — but Fifteensquared have:
definition: an ancient Greek god anagram/”misspelt” of (such)*, after reversal/”return” of CAB=”carriage”
Is turning up with nothing to cut rent twisting? (7)
I haven't cracked this one yet — but Fifteensquared have:
reversal/”turning up” of IS (directly taken from surface), plus O=”nothing; both inside (“to cut” into) TORN=”rent”
See 24
Love, jumpy but not very demanding (7)
I haven't cracked this one yet — but Fifteensquared have:
O=zero=”Love” + NER-[v]-OUS=”jumpy” minus ‘v’ for “very”
Stupid person, American, becomes an emperor (5)
20d
Climatology possibly makes Chinese react badly (5,7)
Type letters or click words in the clue