Jagged cliff (4)
I believe the answer is:
crag
'jagged cliff' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for crag that I've seen before include "Steep rocky cliff" , "Steep rock, peak" , "Steep, rugged peak" , "Rough, steep rock face" , "Steep rugged rock or cliff" .)