Many papers have been impressed by it (9)
I believe the answer is:
watermark
'many papers' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'been impressed by it' is the wordplay.
I cannot quite see how this works, but
'by' could be 'at' and 'at' is found in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'have' acts as a link.
Can you help me to learn more?
(Other definitions for watermark that I've seen before include "Design in paper" , "Paper manufacturer's identification" , "faint pattern" , "Security device, on paper" , "Line showing maximum flood level" .)