Governor's rejection (4)
I believe the answer is:
veto
'governor's rejection' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for veto that I've seen before include "Refuse to authorise" , "The right to forbid an action" , "Literally, 'I forbid'" , "bar" , "Vote that blocks a decision" .)