Fish found on a closure (4)
I believe the answer is:
coda
'closure' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'fish found on a' is the wordplay.
'fish' becomes 'cod' (type of fish).
'found on' says to put letters next to each other.
'cod'+'a'='CODA'
Can you help me to learn more?
(Other definitions for coda that I've seen before include "noted conclusion" , "Word that modifies" , "tail" , "Tailpiece" , "Closing passage of musical piece" .)