Authoritarian Conservative is brought in quickly (7)
I believe the answer is:
fascist
'authoritarian' is the definition.
(thesaurus)
'conservative is brought in quickly' is the wordplay.
'conservative' becomes 'C' (abbreviation commonly used in UK politics).
'brought in' indicates putting letters inside.
'quickly' becomes 'fast' (synonyms).
'c'+'is'='cis'
'cis' put inside 'fast' is 'FASCIST'.
(Other definitions for fascist that I've seen before include "Extreme right-winger" , "Neo-Nazi" , "on the right wing" , "Right-wing extremist" , "Authoritarian right-winger" .)