Religious composition for voices and orchestra (8)
I believe the answer is:
oratorio
'religious composition for voices and orchestra' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oratorio that I've seen before include "Work performed by choir" , "Composition for voices and orchestra, often with biblical theme" , "Large-scale choral work" , "Eg, The Seasons (Haydn)" , "Story set to music" .)