Piece of music without voices (12)
I believe the answer is:
instrumental
'piece of music without voices' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for instrumental that I've seen before include "Acting as a means; piece of music without vocals" , "Important" , "Like a musical piece - it's of help" , "doing without singers" , "Helpful; composition" .)