A quantity of beef on the shelf (5)
I believe the answer is:
aside
'beef on the shelf' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'a quantity' is the wordplay.
'quantity' becomes 'side' (I can't justify this - if you can you should believe this answer much more).
'a'+'side'='ASIDE'
'of' is the link.
Can you help me to learn more?
(Other definitions for aside that I've seen before include "Actor's remark for the audience alone" , "(Pushed) out of the way" , "Remark by an actor, directly to audience say" , "Apart; incidental remark" , "Out of other people's hearing" .)