Flatter fizzy drinks for the audience (4)
I believe the answer is:
coax
'flatter' is the definition.
(I've seen this before)
'fizzy drinks for the audience' is the wordplay.
'fizzy drinks' becomes 'cokes' (Coca Colas).
'for the audience' shows a homophone (sound like).
'cokes' sounds like 'COAX'.
(Other definitions for coax that I've seen before include "Get round" , "Carefully manipulate" , "Persuade; type of cable" , "Inveigle" , "attempt to influence" .)