One fled the country (4)
I believe the answer is:
iran
'country' is the definition.
(Iran is a country)
'one fled' is the wordplay.
'one' becomes 'i' (Roman numeral).
'fled' becomes 'ran' (ran away).
'i'+'ran'='IRAN'
'the' is the link.
(Other definitions for iran that I've seen before include "Modern Persia (4)" , "Country to east of Iraq" , "Tehran is its capital" , "Country of western Asia" , "It was known as Persia until 1935" .)