Permission to abandon (5)
I believe the answer is:
leave
This clue is a double definition.
'permission' is the first definition.
(leave is permission or authorisation)
'abandon' is the second definition.
(to abandon something is to leave it behind)
'to' is the link.
(Other definitions for leave that I've seen before include "Time off, depart" , "Depart on job holiday" , "Depart on work holiday?" , "Deposit" , "Pull out" .)