By it one develops feeling for character (7)
I believe the answer is:
braille
'character' 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 can't see?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for braille that I've seen before include "Touching letters" , "French educationist" , "System of writing for the visually-impaired" , "Language using touch" , "Liberal language for blind people" .)