Country in Africa miles north of a large island (4)
I believe the answer is:
mali
'country in africa' is the definition.
(African nation)
'miles north of a large island' is the wordplay.
'miles' becomes 'm' (common abbreviation).
'north of' is a charade indicator (letters next to each other) (in a down clue, some letters go above others).
'large' becomes 'L' (eg in clothes sizes).
'island' becomes 'i' (geographical abbreviation).
'm'+'a'+'l'+'i'='MALI'
(Other definitions for mali that I've seen before include "African country, former French colony" , "West African country, capital Bamako" , "African country, once French Sudan" , "Country of West Africa" , "part of Africa" .)