Not a whisper to the audience! (5)
I believe the answer is:
aside
'the audience' is the definition.
The answer and definition 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?
'not a whisper' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
The remaining letters 'side' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'to' acts as a 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" , "Quiet words spoken" , "Privately, apart" , "I.e. sad (anag.)" , "Actor's covert line" .)