Outbids American wallies, extreme characters taken in (7)

I believe the answer is:

gazumps

'outbids' is the definition.
(to gazump someone is to outbid them)

'american wallies extreme characters taken in' is the wordplay.
'american wallies' becomes 'gumps' (US term for a foolish person).
'extreme characters' becomes 'AZ' (letters at the extremes of the alphabet).
'taken in' is an insertion indicator.
'gumps' enclosing 'az' is 'GAZUMPS'.

(Another definition for gazumps that I've seen is " Does house-buyer".)

I've seen this clue in The Guardian.

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