Permitting the renting of properties (7)
I believe the answer is:
I believe this is a double definition.
'permitting' is the first definition.
('let' can be a synonym of 'permit')
'renting of properties' is the second definition.
(eg letting a house out)
'the' acts as a link.
(Other definitions for letting that I've seen before include "activity in the property market" , "Renting out; allowing" , "Allowing or leasing" , "Leasing (a property)" , "Dealing with property" .)