15 down: Increases cocaine? What nerve (9)
A fine piece of DA humour: cocaine? what nerve = snow balls = snowballs = increases.
8 down: Major influence for performer under Mick’s band mate, say (3, 6)
I confused myself thinking that this was key figure and the performer referred to Midge Ure somehow. The clue wasn’t quite as difficult as that, and the reference to Keith Richards’ more popularly pronounced name makes this Gold: performer under Mick’s band mate, say = actor under keef, say = keyf actor = key factor = major influence.
24 down: Small 30cm screen (4)
How does DA come up with such misleading sentence meanings? Awesome: small 30cm = s + 1 foot = sift = screen.
1 down: Medieval barmaid switched beer taps? (5)
Another masterly-constructed and misleading sentence meaning: switched beer taps = switched new ch = wench = medieval barmaid.
6 down: Such a turnout rubbish ratbag (7)
Another inventive DA wordplay: such a turnout rubbish = such u out rubbish = sch muck = schmuck = ratbag.