In sweet wine, it's double (4)
I believe the answer is:
twin
'double' is the definition.
(thesaurus)
'in sweet wine it's' is the wordplay.
'in' indicates a hidden word.
'TWIN' is hidden within 'sweet wine ts'.
(Other definitions for twin that I've seen before include "One of an identical pair" , "Castor or Pollux?" , "Balearic island" , "Identical sibling" , "indistinguishable from the next?" .)