Clues are in alphabetical order of their solutions, which are fitted in the grid, jigsaw-wise.
A Another Fine Mess: FIRST NAME ONE SHE (anag) [Oliver & Hardy short film]
B Brindisi: double def
C cutlass: SALT (rev) in CUS(p)
D Dumfries: DUM(as) FRIES
E elan: (th)E)/(powerful)L/(Teqil)A/(Mexica)N
F felicitate: F<ELICIT>ATE
G ground plan: GROUND (in little bits) + PLAN(t)
H haft: (s)HAFT
I Imogen: (l)IMOGE(s) + (deception)N
J Jelly Roll Morton ROLL/M(ale) in JELLY (setter] & (Joe) ORTON
K Klein bottle: LITTLE B(its) ONE (anag) after K (1,000)
L lottery: (f)L<OTTER>Y [no effin’]
M meringue: U in GREEN I’M (anag)
N Nader: REDAN (rev) [Ralph Nader]
0 one tenth: ON + TENT in EH?
P ploy: LO(r-r)Y after P(arking)
Q quinine: QUIN<1>IN + E [The Mighty Quinn, Manfred Mann]
R rennet TENNER (rev)
S sebum: S(pong)E + BUM [to sponge]
T thriving: TH<RIV(e)>ING
U ulcer: paUL CERtainly (hidden)
V vowels: V(ery) + E(ccentric) in OWLS
W womb: WOMB(le) [Wombles of Wimbledon Common]
X xoanon: OX (rev) + ANON
Y yoghurts: YOG(a) HURTS
Z zero-sum: Z + EROS + UM