Irish poetry needing no introduction (4)
I believe the answer is:
erse
'irish' is the definition.
(I've seen this before)
'poetry needing no introduction' is the wordplay.
'poetry' becomes 'verse' ('verse' can be a synonym of 'poetry').
'needing no introduction' means to remove the first letter.
'verse' with its initial letter removed is 'ERSE'.
(Other definitions for erse that I've seen before include "Old Gaelic for the seer" , "Name sometimes given to languages of the Celts in Ireland and Scotland" , "Old Scots or Irish Gaelic" , "Old name for Celtic languages" , "Old language spoken by strange seer" .)