Certain such things will be passed on! (12)

I believe the answer is:

unanswerable

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'on' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?

I can't explain the remainder of the clue.

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(Another definition for unanswerable that I've seen is " Irrefutable".)

I've seen this clue in The Times.

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