Neck of land (7)
I believe the answer is:
isthmus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">neck of land</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for isthmus that I've seen before include "Narrow strip of land connecting two larger areas" , "Narrow land bridge" , "Such a narrow area" , "Tongue" , "Strip of land connecting larger land masses with water on either side" .)