Reversing vehicles? That's clever! (5)
I believe the answer is:
smart
'that's clever' is the definition.
(similar in meaning)
'reversing vehicles?' is the wordplay.
'reversing' shows that the letters should be reversed in order.
'vehicles?' becomes 'trams' (tram is a kind of vehicle).
'trams' backwards is 'SMART'.
(Other definitions for smart that I've seen before include "Quick; tidy; sting" , "Stylish; sting" , "Chic; sting" , "Alick" , "Intelligent; clean, tidy" .)