Rubber wheel rim (4)
I believe the answer is:
tyre
'rubber wheel rim' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tyre that I've seen before include "Rubber wheel rim" , "Ancient city (made of rubber?)" , "Rubber wheel; port" , "Seaport once famed for its purple dye" , "Rubber surround on a wheel" .)