To him, we may sound agreeable (9)
I believe the answer is:
frenchman
'to him we may sound agreeable' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'to him' is the wordplay.
'to' becomes 'french' (I can't justify this - if you can you should give a lot more credence to this answer).
'him' becomes 'man'.
'french'+'man'='FRENCHMAN'
Can you help me to learn more?
(Other definitions for frenchman that I've seen before include "Nice chap" , "Monsieur is one" , "for whom we must be sixteen [NOUS]?" .)