Cliff shows sign of injury (4)
I believe the answer is:
scar
This clue is a double definition.
'cliff' is the first definition.
(thesaurus)
'sign of injury' is the second definition.
(I've seen this before)
'shows' acts as a link.
(Other definitions for scar that I've seen before include "Mark of healed cut" , "Mark from a wound left on the skin" , "One left after having wound" , "Visible mark of healing" , "Gordale - - , Yorks" .)