Composer starts idea, occasionally (5)
I believe the answer is:
satie
'composer' is the definition.
(French composer Erik Satie)
'starts idea occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'starts'+'idea'='startsidea'
The alternate letters of 'startsidea' are 'SATIE'.
(Other definitions for satie that I've seen before include "French composer (Trois Gymnopedies)" , "creative Frenchman" , "scorer" , "French composer of the Gymnopedies, d. 1925" , "posed by yours truly close to stage" .)