Deep narrow gorge (6)
I believe the answer is:
ravine
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deep narrow gorge</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 ravine that I've seen before include "Deep narrow gorge with steep sides" , "'Deep, steep valley (6)'" , "Narrow, steep-sided valley" , "Vainer in narrow gorge" , "Deep narrow valley" .)