Cantata composer (4)
I believe the answer is:
bach
'cantata composer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bach that I've seen before include "musician" , "dear to the Welsh" , "Goldberg Variations composer, d. 1750" , "Welsh term of endearment" , "JS --, baroque composer" .)