Clef type (6)
I believe the answer is:
treble
'clef type' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for treble that I've seen before include "High boy's singing voice" , "Chorister; multiply by three" , "high frequency" , "Member of choir" , "Consisting of three parts; voice" .)