1 across: So-called nerve shown by single alpine heroine (5)
I’m supposing alpine heroine = heidi even though I don’t know why, just like I don’t know why so-called nerve shown by single = heidi.
9 across: Love tie-clip reflection (3)
Here, love = nil. Other than that, I’ve got nothing.
10 across: 1000-kilo van has elastic arm (11)
Kalashnikov = arm, but the rest I can’t explain.
12 across: Leave senseless tenants astride a fence (6)
Leave senseless = deafen, which I suppose means tenants astride a fence = deafen makes little sense to me.
24 across: Help outspoken one proverbially pleased by cruel blow (6, 5)
Cruel blow = sucker punch, but I can’t work out the rest.
2 down: Unorganised assassin edges away, cracked (3-8)
I’m supposing ill-equipped = unorganised, but I can’t figure anything else out.
3 down: Two almost abandoned flash notion (7)
Does inkling = flash notion, or does inkling = notion? Either way, I can’t explain the rest.
8 down: Quiet about happening in itchy year? (7)
Here, itchy year = seventh (as in seven-year itch), but the rest beats me.
14 down: Rearrange a place for subconscious thought? (4, 6)
I’m supposing a place for subconscious thought = back burner, but rearrange = back burner? What?
19 down: Skied ball he’d altered (7)
Altered = morphed, so I’m supposing he’d = hed, but how does skied ball = morp?
23 down: Petty crim and illegal bookie meeting at four (4)
Petty crim = spiv and four = iv, but I don’t get illegal bookie = sp.
25 down: Mongrel PM can go (3)
Mongrel = cur, but I have nothing for PM can go = cur.