Arrogate (5)
I believe the answer is:
usurp
'arrogate' is the definition.
(I know that arrogate can be written as usurp)
This is the entire clue.
(Other definitions for usurp that I've seen before include "Seize wrongfully" , "Take (power etc) illegally" , "Seize without right" , "Seize power illegally" , "Take control of without authority" .)