Crossword Genius

It's very clear that simple task will not be limited to twenty-four hours (5,2,3)

Ross

I believe the answer is:

plain as day

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'clear that simple task will not be limited to twenty-four hours' is the definition.
'plain as day' can be an answer for 'clear' (thesaurus). I'm not sure about the rest of the definition.

I don't understand the remainder of the clue.

Can you help me to learn more?

I've seen this clue in The Irish Times.
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