Talk in Barnet loose (6)
I believe the answer is:
banter
'talk in' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'barnet loose' is the wordplay.
'loose' indicates an anagram (letters are loosened from their original positions).
'barnet' with letters rearranged gives 'BANTER'.
Can you help me to learn more?
(Other definitions for banter that I've seen before include "Action of making use of something" , "Humorous ridicule" , "Light-hearted chaff or teasing" , "Good-natured teasing" , "Light raillery" .)