Awkward sums hit a strip of land (7)
I believe the answer is:
isthmus
'a strip of land' is the definition.
(I've seen this before)
'awkward sums hit' is the wordplay.
'awkward' indicates anagramming the letters.
'sums'+'hit'='sumshit'
'sumshit' is an anagram of 'ISTHMUS'.
(Other definitions for isthmus that I've seen before include "Connective strip of land" , "Narrow land bridge" , "Narrow neck of land joining two larger portions" , "Narrow strip of land with water on two sides" , "Narrow strip linking two larger areas of land" .)