Vehicle, not even brown or black? (6)
I believe the answer is:
carbon
'black?' is the definition.
(thesaurus)
'vehicle not even brown' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'not even' indicates alternate letters (remove even-numbered letters).
The alternating letters of 'brown' are 'bon'.
'car'+'bon'='CARBON'
'or' is the link.
(Other definitions for carbon that I've seen before include "Eg, diamond or graphite" , "Element of glass" , "Flimsy" , "Charcoal is a form of this element" , "Common element" .)