Imperious car with councillor (a jerk) (10)
I believe the answer is:
autocratic
'imperious' is the definition.
(thesaurus)
'car with councillor a jerk' is the wordplay.
'car' becomes 'auto' (automobile).
'with' is a charade indicator (letters next to each other).
'councillor' becomes 'cr' (abbreviation).
'jerk' becomes 'tic' (jerking movement by the body).
'auto'+'cr'+'a'+'tic'='AUTOCRATIC'
(Other definitions for autocratic that I've seen before include "Totalitarian" , "bossy" , "Unrestrainedly powerful" , "Having absolute power" .)