To love her is quite all right (3)
I believe the answer is:
kay
'all right' is the definition.
The definition suggests a singular noun which matches the answer.
'to love her is quite' is the wordplay.
I cannot really see how this works, but
'quite' could be 'ay' (both can mean 'yes') and 'ay' is present in the answer.
A single letter 'k' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for kay that I've seen before include "K" , "Eleventh letter; girl's name" .)