Mufasa's younger brother (4)
I believe the answer is:
scar
'mufasa's younger brother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for scar that I've seen before include "evidence of damage" , "Steep rock - blemish" , "Mark of old injury" , "Skin blemish - bare crag" , "One left after having wound" .)