High-flown writings (7)
I believe the answer is:
airmail
'high-flown writings' 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?
This is the entire clue.
Can you help me to learn more?
(Other definitions for airmail that I've seen before include "I'm a liar (anag)" , "Speedy deliveries" , "Flying service" , "Quick way to deliver" , "Letter delivery system" .)