Country that has to help Northern Ireland in return (5)
I believe the answer is:
india
'country' is the definition.
(India is an example)
'to help northern ireland in return' is the wordplay.
'to help' becomes 'aid' ('aid' can be a synonym of 'help').
'northern ireland' becomes 'NI' (abbreviation).
'in return' says the letters should be written backwards (return can mean to go backwards).
'aid'+'ni'='aidni'
'aidni' reversed gives 'INDIA'.
'that has' is the link.
(Other definitions for india that I've seen before include "Country; I (radio alphabet)" , "Type of paper, rubber etc" , "IDA in the country?" , "Bollywood's country" , "Code for the letter I" .)