Nonsense about a vehicle being strong (6)
I believe the answer is:
robust
'strong' is the definition.
(associated in meaning)
'nonsense about a vehicle' is the wordplay.
'nonsense' becomes 'rot' (rot can mean nonsense or rubbish).
'about' means one lot of letters goes inside another.
'a vehicle' becomes 'bus' (public transport vehicle).
'rot' going around 'bus' is 'ROBUST'.
'being' is the link.
(Other definitions for robust that I've seen before include "Down-to-earth" , "Full and rich (wine)" , "Forceful" , "Tough!" , "Having a strong constitution" .)