Auto ding (4)
I believe the answer is:
dent
'auto ding' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dent that I've seen before include "Arthur, described by Douglas" , "Impression left by impact" , "Slight hollow" , "Hollow caused by a blow" , "Tend to small indentation" .)