Across
Test one conservative holding back effort diversifying unions (8)
I haven't cracked this one yet — but Fifteensquared have:
EXAM (test) + I (one) C (Conservative) round a reversal (holding back) of GO (effort)
Shakespearean villain trapping maiden for mature monarch, say (5)
I haven't cracked this one yet — but Fifteensquared have:
IAGO (villain in Shakespeare’s ‘Othello’) round M (maiden – cricket) for the mature stage of a monarch butterfly, for instance (say)
Isolated high point providing some satisfaction, but only some (4)
A low place for bargaining is producing indignities (10)
I haven't cracked this one yet — but Fifteensquared have:
A BASEMENT (place for bargaining – ‘bargain basement’) + (‘)S (is)
Rubbish that queen may have to bear (6)
Run in without importance in attractive fashion (8)
Condemned left-winger embracing what's wrong (7)
Take to house from food store very shortly (7)
Guided a returning assistant in state capital (8)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (returning) of LED A (guided a) + AIDE (assistant)
Made call that's failed without a line (6)
I haven't cracked this one yet — but Fifteensquared have:
DIED (failed) round A L (a line) – I winced at the spelling then realised, later, that it was essential for the theme
Person whose job is summarising a short book or penning small treatise (10)
I haven't cracked this one yet — but Fifteensquared have:
A B(short book) + OR, from the clue, round S (small) TRACT (treatise)
Creative efforts are raising the stakes, first of all (4)
I haven't cracked this one yet — but Fifteensquared have:
Initial letters (first of all) of Are Raising The Stakes
Perhaps Indian Mutiny's leader imprisoned in end (5)
I haven't cracked this one yet — but Fifteensquared have:
M[utiny] in TAIL (end) – a neat ‘lift and separate’
Reaching crescendo without middle C, like Four Seasons' variations (8)
Down
Push through deep exit frenetically (8)
Site of mausoleum consumed in conflagration (4)
I haven't cracked this one yet — but Fifteensquared have:
Contained in conflAGRAtion – reference to the Taj Mahal, the mausoleum built for his wife by Shah Jahan
Damage politician in one broadcast (6)
Disorganised nonsense in note (7)
Is interrupting the speaker about repeated plea for mercy (8)
I haven't cracked this one yet — but Fifteensquared have:
IS in ME (the speaker) + RE RE (about, repeated) – Latin for ‘have mercy’, repeated often in the liturgy; it’s a lovely word to say or sing, as my choir will be doing often in our ‘Gloria’-themed concert next month
Piano then fiddle I learnt as composer (10)
Accommodation that subsumes second accommodation (6)
I haven't cracked this one yet — but Fifteensquared have:
HOTEL (accommodation) round S (second)
Blue Danube is in this outing – hired Brendan in two cases (6,4)
Twice daily event for island set up, open to change (8)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (set up, in a down clue) of TIDE (twice daily event) + ELBA (island) Edit: or better, as KVa @3 suggests, ‘Twice daily event for island’ = ELBA TIDE
Kind of blue, counterpart of shocking pink? (8)
Supply again includes assorted parts for rockets (7)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (includes assorted parts) of ROCKETS
Be upset when trapped by girlfriend in argument (6)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (upset) of BE in DATE (girlfriend)
Scrambled draw at home – he considered selection, naturally (6)
It's said to accompany a will from home (4)
I haven't cracked this one yet — but Fifteensquared have:
A WAY (as in ‘Where there’s a will, there’s a way’)
Type letters or click words in the clue