Carbonated drink (4)
I believe the answer is:
soda
'carbonated drink' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for soda that I've seen before include "for use with whisky?" , "In the US, a sweet fizzy drink" , "Fizzy drink - chemical compound" , "Alkaline substance used in cleaning, drinks etc" , "Accompaniment to whisky" .)