It's worn in one's car for warmth (5)
I believe the answer is:
'it's worn' is the definition.
I can't judge whether this defines the answer.
'in one's car for warmth' is the wordplay.
'in' indicates the answer is hidden within the clue.
'SCARF' can be found hidden inside 'ones car for warmth'.
Can you help me to learn more?
(Other definitions for scarf that I've seen before include "Item worn on head or shoulders" , "One round neck; a wood joint" , "bit of football memorabilia?" , "Something worn around the head or neck and shoulders" , "Neck or head wrap" .)