Vehicle part worn round waist (5,4)
I believe the answer is:
spare tyre
'vehicle part' is the definition.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for spare tyre that I've seen before include "Extra weight round one's middle" , "rubber product?" , "Part of corporation" , "It's carried in case of a blow-out" , "sign of over-indulgence?" .)