Rich person in Ithaca developed test for believers (3,2,5)

I believe the answer is:

act of faith

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'test for believers' is the definition.
The definition suggests a singular noun which matches the answer.

'rich person in ithaca developed' is the wordplay.
'rich person' becomes 'toff' (toff can mean a rich or upper-class person).
'in' indicates putting letters inside.
'developed' indicates an anagram.
'ithaca' is an anagram of 'acaith'.
'toff' going within 'acaith' is 'ACT OF FAITH'.

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(Other definitions for act of faith that I've seen before include "Religious observance" , "Religiously-inspired deed" .)

I've seen this clue in The Times.

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