She's so good, none can match her! (3)
I believe the answer is:
'she's' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for nun that I've seen before include "Woman in Holy Orders" , "nuisance in pine forest" , "Woman in religious order" , "whose son entered Promised Land" , "Convent dweller" .)