Republic had at first two islands (5)
I believe the answer is:
haiti
'republic' is the definition.
(I know that Haiti is a republic)
'had at first two islands' is the wordplay.
'two islands' can mean two substitutions for 'island'.
'at first' says to take the initial letters.
'island' becomes 'ait' (term for a small island).
'island' becomes 'i' (geographical abbreviation).
The first letter of 'had' is 'h'.
'h'+'ait'+'i'='HAITI'
(Other definitions for haiti that I've seen before include "Country occupying part of Hispaniola" , "W. Indies republic on Hispaniola" , "I hit a West Indian island" , "Republic sharing WI isle" , "West part of Hispaniola" .)