Group of musical notes (5)
I believe the answer is:
chord
'group of musical notes' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for chord that I've seen before include "'The Lost - - ' (Sullivan)" , "Combination of musicians" , "Combination of notes sounded in harmony" , "Combination of musical notes" , "line for mathematicians" .)