Raged, being terribly ardent (6)
I believe the answer is:
Here is my best explanation:
'raged' is the definition.
The answer and definition can be both to do with communicating as well as being past participle verbs.
Maybe you can see a link between them that I don't see?
'terribly ardent' is the subsidiary indication.
'terribly' indicates an anagram.
'ardent' anagrammed gives 'ranted'.
'being' is the link.
(Other definitions for ranted that I've seen before include "Talked wildly and angrily", "Went off", "Spoke wildly and incoherently", "Talked wildly, harangued", "Spoke wildly and foolishly", "Declaimed in a loud, self-important way", "Raved, spouted", "Talked wildly and raved", "Spoke wildly and loudly" and "Raved, mouthed off".)