Depose or unseat (4)
I believe the answer is:
oust
I believe this is a double definition.
'depose' is the first definition.
(I've seen this in another clue)
'unseat' is the second definition.
(I've seen this before)
(Other definitions for oust that I've seen before include "Expel from office or position" , "responsible for expulsions" , "Show the door to" , "Send packing" , "Expel - eject" .)