Across
Tough, one novel Sandy's penned? (6)
I haven't cracked this one yet — but Fifteensquared have:
I="one" + NEW="novel"; both penned inside SY (S & Y, S and Y, S and y)
29a
Millionaire briefly plying rich man with lagers (7,6)
London borough behind minister's brief (9)
Say what to do to get that whole number? (5)
Aggravated, son donned trousers (5)
A flower adorning garment for recipient (9)
I haven't cracked this one yet — but Fifteensquared have:
A (from surface) + DEE=river="flow-er" around DRESS="garment"
Hot shower steamy, ultimately (7)
Dead ant less filling, one feeds on termites (6)
I haven't cracked this one yet — but Fifteensquared have:
definition: a species of marsupial, which feeds on termites NUMB="Dead" + A-[n]-T without its middle letter (less its "filling")
Black article scraped off back of sofa bed (6)
2d
Dalliance in essence over, Andrew? I don't believe it! (7,5,5)
Club in there, or bats (5-4)
Encore: a band not entirely welcoming one (5)
I haven't cracked this one yet — but Fifteensquared have:
A (from surface) + GAN-[g]="band not entirely" around I="one"
See 19
Where crumbs may be taken from book in story of a sentence? (4,5)
I haven't cracked this one yet — but Fifteensquared have:
B (book) inside BIRD TALE="story of a sentence?" – 'bird' is slang for a prison sentence
Old English poet meaning to cover page with rhymes, primarily (7)
I haven't cracked this one yet — but Fifteensquared have:
SENSE="meaning" around P (page), plus R-[hymes]
See 4
Down
Drink spiked by staff – sabotage (5,2)
See 19 Across
Flesh from the ocean offered 24 in old song, loosely speaking? (5,4)
I haven't cracked this one yet — but Fifteensquared have:
24 refers to AGAIN, the solution to 24ac WHALE MEET AGAIN, "loosely speaking" sounds like 'We'll Meet Again', as sung by Vera Lynn [wiki]
Noise after composer of noteless music shut up (5,2)
Turn seat, lifting lid (5)
I haven't cracked this one yet — but Fifteensquared have:
[s]-ADDLE="seat" with its top letter/"lid" removed
Lay down rules where supporter is delayed (9)
Poser: one surely won't be missed (6)
Goody-goody above naughty crime (6)
Top career excited father (9)
Ray secures lid on new cocktail (9)
I haven't cracked this one yet — but Fifteensquared have:
MANTA="Ray" as in the fish, around HAT="lid"; plus N (new)
Sweet thing in pub with poisonous atmosphere? (4,3)
Obtain and taste bitter (6)
According to Spooner, cake layer light (7)
I haven't cracked this one yet — but Fifteensquared have:
Spoonerism of BUN="cake" + SEAM="layer" (e.g. a seam of coal underground)
Small nails – a lot (6)
Powerful people announcing the score of the Roman Empire? (5)
Slope initially dropped a shade (5)
I haven't cracked this one yet — but Fifteensquared have:
[c]-AMBER="Slope" with its first letter/"initial" dropped
Type letters or click words in the clue