Reversing vehicles over end of toes hurts! (6)
I believe the answer is:
smarts
'hurts' is the definition.
('smart' can be a synonym of 'hurt')
'reversing vehicles over end of toes' is the wordplay.
'reversing' says the letters should be written in reverse.
'vehicles' becomes 'trams' (tram is a kind of vehicle).
'over' says to put letters next to each other.
'end of' indicates one should take the final letters.
The last letter of 'toes' is 's'.
'trams' back-to-front is 'smart'.
'smart'+'s'='SMARTS'
(Other definitions for smarts that I've seen before include "Aged dandies" , "Stings painfully" , "is painful" , "Feels upset and annoyed" , "Hurts; stings" .)