Unlawful for POTUS to accept 500 (9)

I believe the answer is:

forbidden

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'unlawful' is the definition.
(thesaurus)

'for potus to accept 500' is the wordplay.
'potus' becomes 'biden' (I am not sure about this - if you are sure you should believe this answer much more).
'to accept' indicates putting letters inside.
'n00' becomes 'D' (Roman numeral for n00).
'biden' enclosing 'd' is 'bidden'.
'for'+'bidden'='FORBIDDEN'

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(Other definitions for forbidden that I've seen before include "Disallowed, banned" , "Proscribed" , "not 35 [PERMISSIBLE]" , "Verboten, prohibited" , "Not allowed, banned" .)

I've seen this clue in The Sun.

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