Just leave! (5)
I believe the answer is:
right
I believe this clue is a double definition.
'just' is the first definition.
(similar in meaning)
'leave' is the second definition.
(leave can mean permission or a right)
(Other definitions for right that I've seen before include "Complete" , "Due" , "Prerogative" , "Genuine" , "Conservative - correct" .)