Rent or allow (3)
I believe the answer is:
let
This clue is a double definition.
'rent' is the first definition.
(I've seen this in another clue)
'allow' is the second definition.
(I know that allow is a more specific form of allow)
(Other definitions for let that I've seen before include "Allow; tennis fault" , "Rent out: grant" , "Allow; permit" , "Reason for scrubbing service" , "& 15 Triple (anag.)" .)