Rector, entering bar, selected text (7)
I believe the answer is:
excerpt
'selected text' 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?
'rector entering bar' is the wordplay.
'rector' becomes 'r'.
'entering' indicates putting letters inside.
'bar' becomes 'except' (both can mean 'not including').
'r' inserted inside 'except' is 'EXCERPT'.
Can you help me to learn more?
(Other definitions for excerpt that I've seen before include "Selected passage from larger work" , "Just a few words" , "1D [CLIP]" , "A passage from, music or book" , "Piece (of music or book)" .)