Land changed into sea (7)
I believe the answer is:
estonia
'land' is the definition.
(Estonia is a country)
'changed into sea' is the wordplay.
'changed' is an anagram indicator.
'into'+'sea'='intosea'
'intosea' is an anagram of 'ESTONIA'.
(Other definitions for estonia that I've seen before include "So eat in here in Eastern Europe" , "Country on the Baltic Sea" , "Nation" , "East European country" , "One of the Baltic States" .)