Hit small vehicle (6)
I believe the answer is:
struck
'hit' is the definition.
(strike can mean to hit)
'small vehicle' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'vehicle' becomes 'truck' (truck is a kind of vehicle).
's'+'truck'='STRUCK'
(Other definitions for struck that I've seen before include "Hit - withheld labour" , "Hit, knocked with blow" , "Given blows - affected instantaneously" , "dismantled" , "Impressed with, as by blow?" .)