When reversing it makes wine (4)
I believe the answer is:
asti
'wine' is the definition.
(I've seen this before)
'when reversing it' is the wordplay.
'when' becomes 'as'.
'reversing' shows that the letters should be reversed in order.
'it' in reverse letter order is 'ti'.
'as'+'ti'='ASTI'
'makes' is the link.
(Other definitions for asti that I've seen before include "Italian town, famous for its wine" , "Italian 'sparkler'" , "town in Italy" , "It's a (anag) - wine" , "Capital of a north-west Italian province, known for its sparking wine" .)