With rough sharp points (6)
I believe the answer is:
jagged
'with rough sharp points' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for jagged that I've seen before include "With a sharply uneven edge" , "Having uneven edge, knife or rock" , "Having outline with sharp projections" , "Of blade, uneven with sharp projections" , "Having a sharply uneven surface or outline" .)