Bob says misfortune is catastrophic - and you can't argue (2,3,4,2,6)

I believe the answer is:

no ifs buts or maybes

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'bob says misfortune is catastrophic and you can't argue' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'bob says misfortune is catastrophic' is the wordplay.
'is catastrophic' is an anagram indicator.
'bob'+'says'+'misfortune'='bobsaysmisfortune'
'bobsaysmisfortune' is an anagram of 'NO IFS BUTS OR MAYBES'.

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I've seen this clue in The Independent.

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