It's bound to be read (4)
I believe the answer is:
book
'read' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for book that I've seen before include "Written work; reserve" , "Hardback, say" , "See 1 ac" , "Reserve - volume" , "Quick work" .)