Shows rank subservience (7)
I believe the answer is:
salutes
'shows' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Perhaps you can see an association between them that I don't see?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for salutes that I've seen before include "Brief inspection" , "Military greetings" , "Greets" .)