Injury memento (4)
I believe the answer is:
scar
'injury memento' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for scar that I've seen before include "Mark left by old wound" , "showing effect of damage to body" , "Permanent mark left by a wound" , "Bare rocky cliff - injury" , "Mark of healed cut" .)