Can of fizzy cocktail (7)
I believe the answer is:
slammer
This could be a double definition.
'can' is the first definition.
(I've seen this in another clue)
'fizzy cocktail' is the second definition.
'slammer' can be an answer for 'cocktail' (eg an Alabama slammer). I am not certain 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)" .)