1 across: She cleaned standpipe, wasting seconds
Not a particularly memorable clue, but I like the reference to Sadie, the Cleaning Lady (standpipe wasting seconds = sadie = she cleaned.)
1 down: Nemo’s dog, perhaps, heard with less frequency?
This one’s funny if not completely neat. Nemo’s dog, perhaps = subwoofer = dog, perhaps, heard with less frequency?.
18 down: Stock-taker fond of crackling?
Nice double meaning clue, with fond of crackling? = rustler = stock-taker.