Slack curtailed probable chance of failure (10,4)

I believe the answer is:

calculated risk

I'm a little stuck... Click here to teach me more about this clue!

'chance of failure' is the definition.
'calculated risk' can be an answer for 'chance' (thesaurus). I'm unsure of the 'of failure' bit.

'slack curtailed probable' is the wordplay.
'slack curtailed' anagrams to 'CALCULATED RISK'.
However, I'm not clear how this is indicated.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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