Composer left after wild party (5)
I believe the answer is:
ravel
'composer' is the definition.
(I've seen this before)
'left after wild party' is the wordplay.
'left' becomes 'l' (common abbreviation).
'after' is a charade indicator (letters next to each other).
'wild party' becomes 'rave' (I've seen this before).
'l' put after 'rave' is 'RAVEL'.
(Other definitions for ravel that I've seen before include "French composer, Maurice (1875-1937)" , "Composer of the orchestral piece, Bolero, d. 1937" , "note-writer observed" , "He scored" , "Fray; composer" .)