Fliers or fatheaded convicts!
I believe the answer is:
flags
'fliers' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Maybe there's an association between them I don't understand?
'fatheaded convicts' is the wordplay.
'fatheaded' becomes 'f' (this might be a standard abbreviation which I don't know about).
'convicts' becomes 'lags' (I've seen this before).
'f'+'lags'='FLAGS'
'or' is the link.
Can you help me to learn more?
(Other definitions for flags that I've seen before include "Banners" , "Declines" , "Paving stones" , "Tires; national symbols" , "Droops" .)