Oh, her? She sounds a bit of all right! (3)
I believe the answer is:
'bit of all right' is the definition.
The definition suggests a singular noun which matches the answer.
'oh her? she sounds a' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
The remaining letters 'ky' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for kay that I've seen before include "K" , "Eleventh letter; girl's name" .)