Crossword Genius

The man upstairs just recognises what the future holds, as the saying goes (3,4,5)

Ross

I believe the answer is:

god only knows

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'the man upstairs' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'just recognises what the future holds as the saying goes' is the wordplay.
I cannot quite see how this works, but
'just' could be 'only' (synonyms) and 'only' is found within the answer.
'recognises' could be 'knows' (know can mean to recognise someone) and 'knows' is found within the answer.
The remaining letters 'god' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Irish Times.
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