Crossword Genius

Hiding? How come? (4,3)

Ross

I believe the answer is:

what for

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This could be a double definition.

'hiding?' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'how come?' is the second definition.
(I've seen this in another clue)

Can you help me to learn more?

(Other definitions for what for that I've seen before include "Punishment that may be given" , "reprimand?" , "it's a question of purpose" , "Beating" .)

I've seen this clue in The Times.
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