Land drifting into sea (7)
I believe the answer is:
estonia
'land' is the definition.
(Estonia is a country)
'drifting into sea' is the wordplay.
'drifting' indicates anagramming the letters.
'into'+'sea'='intosea'
'intosea' is an anagram of 'ESTONIA'.
(Other definitions for estonia that I've seen before include "Baltic republic, capital Tallinn" , "So eat in about here in Northern Europe" , "'So eat in here in Tallinn, say (7)'" , "Country due S. of Finland" , "On a site (anag)" .)