Just say no, it must be returned by the soldiers (7)
I believe the answer is:
mention
'just say no' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'it must be returned by the soldiers' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'must' becomes 'noi' (I can't justify this - if you can you should give a lot more credence to this answer).
'be returned' says the letters should be written in reverse (I've seen 'being returned' mean this).
'by' is a charade indicator (letters next to each other).
'the soldiers' becomes 'men' (I've seen this before).
'noi' backwards is 'ion'.
't'+'ion'='tion'
'tion' put after 'men' is 'MENTION'.
Can you help me to learn more?
(Other definitions for mention that I've seen before include "Briefly refer to (something)" , "Allude to" , "Make reference to" , "Remark" , "Cite; quote" .)