Permission, permit (7)
I believe the answer is:
licence
This clue is a double definition.
'permission' is the first definition.
(I've seen this before)
'permit' is the second definition.
(I know that licence is a more specific form of authorise)
(Other definitions for licence that I've seen before include "Leave" , "Authority - or freedom!" , "Authority (or the lack of it!)" , "Permit to operate" , "Driving permit" .)