Allow to rent out (3)
I believe the answer is:
let
This clue is a double definition.
'allow to' is the first definition.
(I've seen this in another clue)
'rent out' is the second definition.
(I've seen this before)
(Other definitions for let that I've seen before include "Permit; lease" , "Service that must be repeated" , "Was inclined to ignore" , "Allow - hire" , "Reason for scrubbing service" .)