Man seen in the car is a body (7)
I believe the answer is:
cadaver
'body' is the definition.
(I know that body can be written as cadaver)
'man seen in the car' is the wordplay.
'man' becomes 'dave' (I've seen this before).
'seen in' indicates putting letters inside.
'dave' placed inside 'car' is 'CADAVER'.
'is a' acts as a link.
(Other definitions for cadaver that I've seen before include "Human body dissected by medical students" , "Stiff" , "Dead body, corpse" , "Remains of a human" , "A kind of corpse" .)