Jagged mountain range (6)
I believe the answer is:
sierra
'jagged mountain range' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sierra that I've seen before include "Nato alphabet 'S'" , "Range of mountains with jagged peaks" , "Long range" , "Jagged mountains - code word for S" , "Comms code S" .)