Fizzy drink, cold or not, initially it's enjoyed at the cinema? (7)
I believe the answer is:
popcorn
'it's enjoyed at the cinema?' is the definition.
'fizzy drink cold or not initially' is the wordplay.
'fizzy drink' becomes 'pop' (I've seen this before).
'cold' becomes 'c' (eg on taps).
'initially' says to take the initial letters.
The initial letter of 'not' is 'n'.
'pop'+'c'+'or'+'n'='POPCORN'
(Other definitions for popcorn that I've seen before include "Stuff to eat at the cinema" , "At the cinema something to get through" , "Popular snack in the cinema" , "modified maize" , "Popular cinema food" .)