Box of fizz unwrapped (6)
I believe the answer is:
Here is my best explanation:
'box' is the definition.
'fizz unwrapped' is the wordplay.
'fizz' becomes 'champers' (both are informal terms for champagne).
'unwrapped' means to look at the middle letters (the letters which wrap the word are removed).
The middle of 'champers' is 'HAMPER'.
'of' is the link.