Idiot sues bizarrely, promoting disorder (9)
I believe the answer is:
seditious
'promoting disorder' is the definition.
'idiot sues bizarrely' is the wordplay.
'bizarrely' is an anagram indicator.
'idiot'+'sues'='idiotsues'
'idiotsues' anagrammed gives 'SEDITIOUS'.
(Other definitions for seditious that I've seen before include "Revolutionary" , "Inciting to revolt" , "inciting rebellion" , "Subversive" , "Rabble-rousing" .)