It's a flipping fizzy wine (4)
I believe the answer is:
asti
'fizzy wine' is the definition.
(I've seen this before)
'it's a flipping' is the wordplay.
'flipping' is a reversal indicator.
'its'+'a'='itsa'
'itsa' in reverse letter order is 'ASTI'.
(Other definitions for asti that I've seen before include "Italian wine - (then change a letter for ...)" , "- spumante, It. wine" , "Italian 'sparkler'" , "18" , "Piedmontese white wine" .)