Diamond of music (4)
I believe the answer is:
neil
'diamond of music' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for neil that I've seen before include "-- Armstrong, Apollo astronaut" , "One of 14 DIAMONDS] 's" , "1969 moon walker" , "- Simon, US dramatist (Barefoot in the Park)" , "-- Sedaka, US singer" .)