A marine trained in the country (7)
I believe the answer is:
armenia
'the country' is the definition.
(Armenia is a country)
'a marine trained' is the wordplay.
'trained' indicates an anagram (to train can mean to grow something into a shape).
'marine' anagrammed gives 'rmenia'.
'a'+'rmenia'='ARMENIA'
'in' is the link.
(Other definitions for armenia that I've seen before include "Country in the Caucasus, capital Yerevan" , "South-west Asian country, capital Yerevan" , "Republic, formerly part of the Soviet Union" , "Landlocked country of southwest Asia" , "Landlocked country, an Asian soviet before 1991, capital Yerevan" .)