Turn sea into land (7)
I believe the answer is:
estonia
'land' is the definition.
(Estonia is a country)
'turn sea into' is the wordplay.
'turn' is an anagram indicator.
'sea'+'into'='seainto'
'seainto' is an anagram of 'ESTONIA'.
(Other definitions for estonia that I've seen before include "So eat in about here in Northern Europe" , "So eat in poorly on the Baltic Sea" , "Republic in northeastern Europe" , "Country due S. of Finland" , "Nation" .)