Permission to exit (5)
I believe the answer is:
leave
I believe this is a double definition.
'permission' is the first definition.
(leave is permission or authorisation)
'exit' is the second definition.
(I know that exit can be written as leave)
'to' acts as a link.
(Other definitions for leave that I've seen before include "Permission to take a vacation" , "Depart - on authorised holidays?" , "Abandon" , "Time off; go" , "Break" .)