American genius creates knock out current account (8)

I believe the answer is:

brainiac

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'american genius' is the definition.
'brainiac' can be an answer for 'genius' (I've seen this in another clue). I am not certain of the 'american' bit.

'knock out current account' is the wordplay.
'knock out' becomes 'brain' (I can't explain this - if you can you should believe this answer much more).
'current' becomes 'I' (symbol for electric current).
'account' becomes 'ac' (abbreviation for account).
'brain'+'i'+'ac'='BRAINIAC'

'creates' is the link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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