Small vehicle showing sign of damage (4)
I believe the answer is:
scar
'sign of damage' is the definition.
(I've seen this before)
'small vehicle' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'vehicle' becomes 'car' (car is a kind of vehicle).
's'+'car'='SCAR'
'showing' acts as a link.
(Other definitions for scar that I've seen before include "Visible mark of healing" , "Mark from a wound left on the skin" , "One left after having wound" , "Bare rocky cliff - injury" , "Sign of wound" .)