Such a person may not use his tongue when speaking (9)
I believe the answer is:
bilingual
'such a person may not use his' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'tongue when speaking' is the wordplay.
I cannot really understand how this works, but
'tongue' could be 'lingua' (synonyms) and 'lingua' is found in the answer.
The remaining letters 'bil' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bilingual that I've seen before include "Able to speak two languages" , "having two tongues" , "Adept in two languages" , "Speaking two languages" , "Like interpreter" .)