Screwball home for the kernel (7)

I believe the answer is:

nutcase

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'screwball' is the definition.
(synonyms)

'home for the kernel' is the wordplay.
'home' becomes 'case' (I can't justify this - if you can you should believe this answer much more).
'for' means one lot of letters go next to another (I've seen this in other clues).
'the kernel' becomes 'nut' (I've seen this before).
'case' after 'nut' is 'NUTCASE'.

Can you help me to learn more?

(Other definitions for nutcase that I've seen before include "Crackpot" , "Slang for a crazy person" , "Fruitcake?" , "Slangily, a crazy person" , "Maniac - shell" .)

I've seen this clue in the Sydney Morning Herald.

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