Rubbish wagon overturning farm vehicle (7)
I believe the answer is:
tractor
'farm vehicle' is the definition.
(vehicle used on a farm)
'rubbish wagon overturning' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'wagon' becomes 'cart' (cart is a kind of wagon).
'overturning' shows that the letters should be reversed in order.
'rot'+'cart'='rotcart'
'rotcart' written backwards gives 'TRACTOR'.
(Other definitions for tractor that I've seen before include "Agricultural vehicle" , "Type of truck with a a cab but no body" , "I can draw" , "Vehicle used on farms" , "Tower" .)