Jagged mountain range (6)
I believe the answer is:
sierra
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">jagged mountain range</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)