Allowed to be occupied (3)
I believe the answer is:
let
I believe this is a double definition.
'allowed to' is the first definition.
(to let something happen is to allow it)
'be occupied' is the second definition.
(I've seen this in another clue)
(Other definitions for let that I've seen before include "Rent out: grant" , "Permit or rent" , "inefficient service" , "Umpire's decision" , "Service that must be repeated" .)