Mostly stressed foreign consonant (3)
I believe the answer is:
tau
'foreign consonant' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'mostly stressed' is the wordplay.
'mostly' means to remove the last letter.
'stressed' becomes 'taut' (I've seen this in other clues).
'taut' with its last letter taken away is 'TAU'.
Can you help me to learn more?
(Other definitions for tau that I've seen before include "letter from foreigner" , "Foreign character" , "character from Athens" , "A subatomic particle" , "Greek letter; cross" .)