Rugged mountain range (6)
I believe the answer is:
sierra
'rugged 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 "that Romeo is not after" , "Long jagged mountain chain" , "Jagged mountain range" , "Jagged mountains - code word for S" , "- Nevada, Spanish mountain range" .)