Composer’s optional direction to play louder? (4)
I believe the answer is:
orff
'composer's' is the definition.
(I've seen this before)
'optional direction to play louder?' is the wordplay.
I cannot really see how this works, but
'direction' could be 'r' (r is abbreviation for right) and 'r' is located in the answer.
The remaining letters 'off' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
(Other definitions for orff that I've seen before include "With all instruments" , "German who scored" , "Composer of Carmina Burana, d. 1982" , "German composer, Carl d. 1982" , "Rowing boat" .)