Nonsense about a vehicle being strong (6)
I believe the answer is:
robust
'strong' is the definition.
(similar in meaning)
'nonsense about a vehicle' is the wordplay.
'nonsense' becomes 'rot' (I've seen this before).
'about' indicates putting letters inside.
'a vehicle' becomes 'bus' (bus is a kind of vehicle).
'rot' placed around 'bus' is 'ROBUST'.
'being' acts as a link.
(Other definitions for robust that I've seen before include "Down-to-earth" , "Full and rich (wine)" , "Forceful" , "Tough!" , "Having a strong constitution" .)