Root cause of a vehicle getting rust on (6)
I believe the answer is:
carrot
'root cause' is the definition.
'carrot' can be an answer for 'root' (I've seen this before). I am not sure about the 'cause' bit.
'a vehicle getting rust on' is the wordplay.
'a vehicle' becomes 'car' (car is a kind of vehicle).
'getting' means one lot of letters go next to another.
'rust on' becomes 'rot' (I am not sure about the 'on' bit.).
'car'+'rot'='CARROT'
'of' is the link.
Can you help me to learn more?
(Other definitions for carrot that I've seen before include "Enticement; vegetable" , "Tapering vegetable" , "orangey colour" , "Obstacle in race" , "Root vegetable" .)