What an escapologist might say — I'm sure of it! (3,2,5)

I believe the answer is:

ill be bound

'i'm sure of it' is the definition.

I can't explain the remainder of the clue.

(Other definitions for ill be bound that I've seen before include "No doubt" , "how Houdini would describe first stage of his routine" , "Certainly" , "I am sure that's true" , "Believe me" .)

I've seen this clue in The Times.

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