Tongue unaffected when turned over (9)
I believe the answer is:
malayalam
'tongue unaffected when turned over' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'tongue unaffected when turned' is the wordplay.
'tongue' becomes 'Malay' ('tongue' can mean a language).
'unaffected' becomes 'mala' (I can't justify this - if you can you should believe this answer much more).
'when turned' says the letters should be written backwards.
'mala' back-to-front is 'alam'.
'malay'+'alam'='MALAYALAM'
Can you help me to learn more?
(Other definitions for malayalam that I've seen before include "Language we don't often hear" , "Indian language" , "Palindromic Far East language" .)