He sings three times (6)
I believe the answer is:
treble
'he sings three times' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
This is all the clue.
Can you help me to learn more?
(Other definitions for treble that I've seen before include "High darts score" , "Threefold; boy's voice" , "High boy's singing voice" , "Feat of winning three major trophies" , "High voice - large drink" .)