Brief shows of resentment, usually (5)
I believe the answer is:
demos
'brief shows' is the definition.
The definition and answer can be both related to communication as well as being plural nouns.
Perhaps you can see a link between them that I don't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for demos that I've seen before include "The populace" , "mass rallies?" , "protests" , "The common people" , "The people (Greek)" .)