In a car, one giving voice to contempt? (6)
I believe the answer is:
hooter
'in' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for hooter that I've seen before include "it smells" , "Factory siren" , "Uphill stone pusher (Gk. myth)" , "Gnomon" , "It makes a loud noise" .)