Possible Clues:

• Prop for Bugs Bunny
• Symbolic incentive
• Symbolic lure
• It's nonsense for the motorist to try to bribe the ass with it
• That's the ruddy root to get the artist back in the vehicle
• Incentive to acquire an auto? Rubbish!
• Incentive; vegetable
• Corrosion under vehicle is an orangey colour
• That might be the ruddy root of the trouble with the end of 16 across
• That's the ruddy root of the trouble with your motor