A better mark (4)
I believe the answer is:
scar
This clue could be a double definition.
'a better' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'mark' is the second definition.
(mark left by an injury)
Can you help me to learn more?
(Other definitions for scar that I've seen before include "Permanent mark left by a wound" , "Limestone cliff or outcrop" , "Steep rock - blemish" , "Craggy rock formation" , "Effect of unpleasant experience" .)