Cut back not definite? (7)
I believe the answer is:
tonsure
'cut' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'back not definite?' is the wordplay.
'back' says the letters should be written backwards.
'definite?' becomes 'sure' ('sure' can be a synonym of 'definite').
'not' reversed gives 'ton'.
'ton'+'sure'='TONSURE'
Can you help me to learn more?
(Other definitions for tonsure that I've seen before include "Monk's haircut" , "Monastic hairstyle" , "Close-shaved hairstyle" , "Uncovered area on top" , "Shaven part of monk's head" .)