Helpful for the orchestra (12)
I believe the answer is:
instrumental
'helpful' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for instrumental that I've seen before include "doing without singers" , "Having some responsibility - not vocal" , "Piece of music without voices" , "case" , "Acting as a means; piece of music without vocals" .)