Scratch or scuff (3)
I believe the answer is:
mar
I believe this clue is a double definition.
'scratch' is the first definition.
(I've seen this in another clue)
'scuff' is the second definition.
(I've seen this in another clue)
(Other definitions for mar that I've seen before include "Cause harm" , "Spoil or deface" , "wreck" , "A windy month" , "Damage; month (abbr.)" .)