On a car, bad rust that's possibly growing (6)
I believe the answer is:
carrot
'rust that's possibly growing' is the definition.
I can't judge whether this definition defines the answer.
'on a car bad' is the wordplay.
'on' is a charade indicator (letters next to each other).
'bad' becomes 'rot' (I've seen this before).
'car' next to 'rot' is 'CARROT'.
Can you help me to learn more?
(Other definitions for carrot that I've seen before include "Orangey vegetable" , "Red vegetable used as inducement" , "veg" , "Root vegetable" , "orangey colour" .)