You can sing this, but please don't! (7)
I believe the answer is:
refrain
This clue could be a double definition.
'you can' is the first definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'sing this but please don't' is the second definition.
The definition suggests a singular noun which matches the answer.
Can you help me to learn more?
(Other definitions for refrain that I've seen before include "Hold back" , "Stop oneself (from doing something)" , "Chorus of a song" , "Cease - repeated phrase" , "Kindly desist - from song?" .)