Part of a car wheel (6)
I believe the answer is:
hubcap
'part of a car wheel' is the definition.
(I know that car wheel is the is part of of hubcap.)
This is all the clue.
(Other definitions for hubcap that I've seen before include "It fits over the central part of a wheel" , "Metal protector for car wheel" , "Cover on a car wheel" , "Protective plate for car wheel" , "Cover for centre of a car's wheel" .)