A line to one side? (5,7)
I believe the answer is:
stage whisper
'side?' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'a line to one' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found in the answer.
'line' could be 'tag' (tag line is a kind of line) and 'tag' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stage whisper that I've seen before include "Actor's aside" , "something the audience should hear" , "Ostensibly private aside intended to be heard by audience" , "Actor's quiet remark meant for the audience to hear" , "Utterance by an actor, supposedly not heard by the other players" .)