Unsaddle (6)
I believe the answer is:
unseat
'unsaddle' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for unseat that I've seen before include "Remove from horse (or house?)" , "Cause to fall from the saddle" , "Dislodge from saddle" , "Throw (as a 15?)" , "Remove from power" .)