Can of fizzy cocktail (7)
I believe the answer is:
slammer
This clue could be a double definition.
'can' is the first definition.
(I've seen this before)
'fizzy cocktail' is the second definition.
'slammer' can be an answer for 'cocktail' (eg an Alabama slammer). I'm unsure of the 'fizzy' bit.
'of' is the link.
Can you help me to learn more?
(Other definitions for slammer that I've seen before include "One severely criticises" , "Prison (colloq.)" , "Prison - critic?" , "He noisily leaves the room" , "Prison (slang)" .)