Sweet, in the style of sweet wine (7)
I believe the answer is:
marsala
'sweet wine' is the definition.
(I've seen this in another clue)
'sweet in the style of' is the wordplay.
'sweet' becomes 'Mars' (brand of chocolate bar).
'in the style of' becomes 'a la' (e.g. chicken a la King).
'mars'+'ala'='MARSALA'
(Other definitions for marsala that I've seen before include "Fortified wine from Sicily" , "Fortified Sicilian wine" , "Wine - as alarm (anag)" , "Dessert wine from Sicily" , "Sweet dessert wine" .)