Handel's "Messiah," for one (8)
I believe the answer is:
oratorio
'handel's messiah for one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oratorio that I've seen before include "Musical composition usually with biblical theme (8)" , "Sung composition based on a religious theme" , "piece of music" , "E.g. Messiah or Elijah" , "I, too, roar at sacred music" .)