Wine forced on Gershwin (7)
I believe the answer is:
madeira
'wine' is the definition.
(I know that Madeira is a type of fortified wine)
'forced on gershwin' is the wordplay.
'forced' becomes 'made' (both can mean coerced).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'gershwin' becomes 'ira' (lyricist Ira Gershwin, brother of George).
'made'+'ira'='MADEIRA'
(Other definitions for madeira that I've seen before include "Fortified Portuguese wine" , "Island in the Atlantic Ocean" , "cake producer" , "Rich, fortified white wine" , "Atlantic territory" .)