Put one's foot down? Minister's revolting (3,2)
'put one's foot down?' is the definition.
(as in to rev a car)
'minister's revolting' is the wordplay.
'minister' becomes 'rev' (I've seen this in other clues).
'revolting' becomes 'up' (I've seen this in other clues).
(Other definitions for rev up that I've seen before include "To create excitement", "Increase the engine speed", "drive to go faster", "Press accelerator", "Gun the engine".)