Wheel-ring (4)
I believe the answer is:
tyre
I believe this is a double definition.
'wheel' is the first definition.
(I've seen this before)
'ring' is the second definition.
(I know that tyre is a type of ring)
(Other definitions for tyre that I've seen before include "Old Phoenician port" , "Wheel cover, may be tubeless" , "Rubber wheel-covering" , "Rubber tube on a wheel" , "A circular cushion" .)