English ad put out by idiot causing division in Ireland (5)
I believe the answer is:
meath
'division in ireland' is the definition.
(county of Ireland)
'english ad put out by idiot' is the wordplay.
I cannot quite understand how this works, but
'english' could be 'e' (abbreviation) and 'e' is present in the answer.
'by' could be 'at' and 'at' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'causing' is the link.
(Other definitions for meath that I've seen before include "County NW of Dublin" , "lost province" , "part of Ireland" , "Irish county of ancient kings, site of Tara" , "Tara's county" .)