Jagged line (6)
I believe the answer is:
zigzag
'jagged line' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for zigzag that I've seen before include "Proceed with sharp, alternating turns" , "Describes a series of short sharp turns" , "Pattern of short, sharp turns" , "Move first one way, then the other" , "Make sharp turns" .)