Neck of land (7)
I believe the answer is:
isthmus
'neck of land' is the definition.
(I've seen this before)
This is the entire clue.
(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" .)