Brother returned short letter to person from Brest (6)
I believe the answer is:
breton
'person from brest' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'brother returned short letter' is the wordplay.
'brother' becomes 'br'.
'returned' shows that the letters should be reversed in order.
'short letter' becomes 'note' (synonyms).
'note' back-to-front is 'eton'.
'br'+'eton'='BRETON'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for breton that I've seen before include "Person from Brittany" , "Inhabitant of NW France" , "from Northern France" , "French language class" , "Surrealist" .)