Watch for one’s authority to be overturned (5)
I believe the answer is:
timer
'watch for one's' is the definition.
(a watch times things)
'authority to be overturned' is the wordplay.
'authority' becomes 'remit' (I've seen this before).
'to be overturned' says the letters should be written backwards.
'remit' reversed gives 'TIMER'.
(Other definitions for timer that I've seen before include "Clocklike actuator" , "Clock or watch" , "Eg, clock" , "Clocklike device" , "Trigger mechanism" .)