Authoritarian is back (5)
I believe the answer is:
stern
I believe this is a double definition.
'authoritarian' is the first definition.
(I've seen this before)
'is back' is the second definition.
(stern means the back of a boat)
(Other definitions for stern that I've seen before include "Rear; severe, serious" , "Unyielding - rump" , "Rents out at rear of boat" , "Strict - forbidding" , "Ship's rear" .)