It's uncouth to jeer Irish leader off (7)
I believe the answer is:
boorish
'it's uncouth' is the definition.
(I've seen this before)
'jeer irish leader off' is the wordplay.
I cannot quite see how this works, but
'jeer' could be 'boo' (I've seen this before) and 'boo' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for boorish that I've seen before include "Uncouth" , "Rude - vulgar - rustic" , "Ill-mannered and insensitive" , "Coarse - ill-mannered" , "Coarse, rough or rude" .)