In Ireland it improved, causing madness (9)

I believe the answer is:

deliriant

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'madness' is the definition.
I know nothing about this answer so I can't judge whether this works.

'in ireland it improved' is the wordplay.
'improved' indicates an anagram.
'ireland'+'it'='irelandit'
'irelandit' with letters rearranged gives 'DELIRIANT'.

'causing' acts as a link.

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I've seen this clue in The Daily Express.

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