Land of the leprechauns (4)
I believe the answer is:
'land of the leprechauns' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for erin that I've seen before include "Let ... Remember (song)" , "'Come back to ...' (emigrant song)" , "The Emerald Isle, in poetry" , "Poetically, Ireland" , "Land" .)