Lack of sympathy for defective state of Old Testament? (12)

I believe the answer is:

ruthlessness

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'lack of sympathy' is the definition.

'defective state of old testament?' is the wordplay.
I cannot quite see how this works, but
'state' could be 'rut' (rut is a kind of state) and 'rut' is located in the answer.
This explanation may well be incorrect...

'for' acts as a link.

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I've seen this clue in The Times.

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