At Iona Bill go crazy? It's morally required? (12)

I believe the answer is:

obligational

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'morally required?' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally mean the same thing.

'at iona bill go crazy?' is the wordplay.
'crazy?' indicates an anagram (I've seen 'crazy' mean this).
'at'+'iona'+'bill'+'go'='ationabillgo'
'ationabillgo' with letters rearranged gives 'OBLIGATIONAL'.

'it's' is the link.

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I've seen this clue in the Sydney Morning Herald.

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