Sea-girt land (4)
I believe the answer is:
isle
'sea-girt land' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for isle that I've seen before include "Eg, Iona" , "cut-off location" , "one has water all round" , "Eg, eyot or inch" , "Man's one" .)