Allow to rent (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' is the second definition.
(I know that rent can be written as let)
(Other definitions for let that I've seen before include "Won't stop you" , "Service that must be repeated" , "Allow; rental period" , "inefficient service" , "& 15 Triple (anag.)" .)