Sweet Italian bubbly (4)
I believe the answer is:
asti
'sweet italian bubbly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for asti that I've seen before include "Italian town, famous for its wine" , "Italian 'sparkler'" , "Italian drunk" , "Fizzy wine" , "Source of fizz" .)