Narrow hilltop (5)
I believe the answer is:
ridge
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">narrow hilltop</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ridge that I've seen before include "Line of higher ground" , "Line of raised ground" , "Long, narrow range of hills" , "there's a lot of pressure in it" , "Wrinkle" .)