Across
Drum almost filled with a fruit (6)
I haven't cracked this one yet — but Fifteensquared have:
A in TOM-TO[m]. “Knowledge is knowing that a tomato is a fruit; wisdom is not putting it in a fruit salad” (Miles Kington)
See 8
Odd tuna swimming round northern river in Russia (9)
I haven't cracked this one yet — but Fifteensquared have:
N in TUNA* + URAL
Beauty pageants uneventful, though some tripping over (5)
See 4 down
Left-leaning Stalinist not quite right after revolution (9)
Shrink once had nurses excited at the outset (3,4)
I haven't cracked this one yet — but Fifteensquared have:
E[xcited] in DID OWN (once had)
Blue essentially follows decoration of room in gold (6)
Echoing note resounding initially — with this? (6)
I haven't cracked this one yet — but Fifteensquared have:
Reverse of BREVE (note) + R[esounding]
Ultimately, buttock and lower back prodded by a couple of unknowns — one's an idiot (7)
I haven't cracked this one yet — but Fifteensquared have:
A + Z Z (mathematical unknowns) in reverse of COW (one that lows) + [buttoc]K
River having dried up on the banks, used a digger (9)
I haven't cracked this one yet — but Fifteensquared have:
R in TOWELLED
Grand nicked by one scoundrel — or another? (5)
I haven't cracked this one yet — but Fifteensquared have:
G in ROUÉ
Future time in firm reviewed (5)
I haven't cracked this one yet — but Fifteensquared have:
T in reverse of REAL (firm)
Fidelio's Léonore, originally in disguise here: well, well, well! (9)
I haven't cracked this one yet — but Fifteensquared have:
Anagram of FIDELIO’S + L[éonore]. Leonore does indeed disguise herself as Fidelio at the start of Beethoven’s opera: I’m not sure why Paul has used the French form of her name here
Collaboration with offender and my Lord on the radio? (7)
Whole testament, account in it (6)
Down
Dull sound when round gong that's fingered (7)
Get out having escaped pea: try fruit (5)
I haven't cracked this one yet — but Fifteensquared have:
MANGE TOUT less GET OUT + GO (try)
Carving on reservation, painted plate needing time for inscription (5,4)
11a
Actor putting the flora in Florida? (7,5)
...s game (5)
Part sung in key, another key briefly eclipsing it (9)
Take stock when philosopher overheard? (6)
I haven't cracked this one yet — but Fifteensquared have:
Homophome of (Bertrand] Russell, with the “stock” being cattle
4a
Inside job? (6,7)
21d
Looking surprised — as a snail? (4,3,2,6)
Brilliant at music, strange being on tour of Australia (9)
Platform where meaty sandwiches left (7)
I haven't cracked this one yet — but Fifteensquared have:
L in BACON-Y
Bottomless den concealed by foxy to a great extent (6)
Youth and king upset about fascist force in parliament (7)
I haven't cracked this one yet — but Fifteensquared have:
SS (Nazi force) in reverse of TEEN + K
See 14
Miss little monster having sliced off head (5)
Type of fruit, one in apple (5)
Type letters or click words in the clue