A country one has entered before (4)
I believe the answer is:
eire
'a country' is the definition.
(I know that Eire is a country)
'one has entered before' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'before' could be 'ere' (poetic term for 'before') and 'ere' is found in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for eire that I've seen before include "EU country" , "Southern Ireland" , "Gaelic name for Republic of Ireland" , "Official name of the Irish Republic, 1937-49" , "Former name for the Republic of Ireland" .)