Polite request for parking rent (6)
I believe the answer is:
please
'polite request' is the definition.
(I've seen this before)
'parking rent' is the wordplay.
'parking' becomes 'p'.
'rent' becomes 'lease' (I've seen this before).
'p'+'lease'='PLEASE'
'for' is the link.
(Other definitions for please that I've seen before include "Polite request - make someone happy" , "Delight; amuse" , "Elapse (anag.)" , "Polite addition to a request" , "Delight, satisfy" .)