African country, one a republic (7)
I believe the answer is:
nigeria
'republic' is the definition.
(I know that Nigeria is a federal republic)
'african country one a' is the wordplay.
'african country' becomes 'niger' (country in Africa).
'one' becomes 'i' (Roman numeral).
'niger'+'i'+'a'='NIGERIA'
(Other definitions for nigeria that I've seen before include "Country bordered by Benin, Niger, Chad, and Cameroon" , "In rage I turn to this country" , "Possible home for African" , "West African state" , "W. African country" .)