Possible Clues:

• Perhaps a doubler in the cot gets to the ruddy root of it
• "An intellectual ___! The mind boggles!" (line from 1951's "The Thing")
• You may take it as read, by the sound of it, that that is one of 30 across, by the sound of it
• Sounds as if precious little weight will make the motor decay
• Incentive to swap rubbish vehicle
• Rust beneath vehicle providing possible incentive
• Bugs Bunny snack
• Pointed vegetable
• Obstacle in race
• Is that the ruddy root of the trouble with the old bus?