Marks vehicles on style, at first (5)
I believe the answer is:
scars
'marks' is the definition.
('scar' can be a synonym of 'mark')
'vehicles on style at first' is the wordplay.
'vehicles' becomes 'cars' (car is a kind of vehicle).
'on' is a charade indicator (letters next to each other).
'style at first' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'cars' put after 's' is 'SCARS'.
Can you help me to learn more?
(Another definition for scars that I've seen is " Marks left by wounds".)