Scathing about triad's part in civil unrest (9)
I believe the answer is:
vitriolic
'scathing' is the definition.
(synonyms)
'triad's part in civil unrest' is the wordplay.
'triad' becomes 'trio' (synonyms).
'part in' indicates putting letters inside (inserted letters form part of the word).
'unrest' indicates an anagram.
'civil' with letters rearranged gives 'vilic'.
'trio' inserted inside 'vilic' is 'VITRIOLIC'.
'about' is the link.
(Other definitions for vitriolic that I've seen before include "biting" , "Acrimonious" , "Severely bitter" , "Filled with malice" , "Bitterly critical" .)