It's a confusing thing to do (5)
I believe the answer is:
blend
'do' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for blend that I've seen before include "Amalgamate" , "Thorough mixture" , "Merge" , "Mix, stir" , "Combine together" .)