Rough or jagged (6)
I believe the answer is:
uneven
I believe this clue is a double definition.
'rough' is the first definition.
(associated in meaning)
'jagged' is the second definition.
(similar in meaning)
(Other definitions for uneven that I've seen before include "Not level or smooth" , "Not uniform or smooth" , "Ill-matched - irregular" , "Rough on the surface" , "Rough, bumpy" .)