One maliciously damaging vehicle, youth going north (6)
I believe the answer is:
vandal
'one maliciously damaging' is the definition.
(someone who damages things or property)
'vehicle youth going north' is the wordplay.
'vehicle' becomes 'van' (van is a kind of vehicle).
'youth' becomes 'lad' (I've seen this in another clue).
'going north' says the letters should be written in reverse.
'lad' reversed gives 'dal'.
'van'+'dal'='VANDAL'
(Other definitions for vandal that I've seen before include "One who damages things maliciously" , "Old German" , "Deliberate destroyer" , "Person causing destruction to property" , "Barbarian - wrecker" .)