Fizzy soft drink (4)
I believe the answer is:
soda
'fizzy soft drink' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for soda that I've seen before include "Type of bread, water or fountain" , "kind of water" , "for use with whisky?" , "Fizzy drink - chemical compound" , "Fizzy water, goes well with whiskey" .)