Large choral work (8)
I believe the answer is:
oratorio
'large choral work' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for oratorio that I've seen before include "Music for many performers" , "Composition for singers and orchestra" , "Musical work for orchestra and voices" , "Eg, Walton's Belshazzar's Feast" , "E.g. Messiah or Elijah" .)