A singer of three? (6)
I believe the answer is:
treble
'a singer' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for treble that I've seen before include "Three times - a boy soprano" , "What boys sing" , "Multiple score in darts" , "High voice - large drink" , "Chorister; multiply by three" .)