Assist Argentina's foremost banker, say (4)

I believe the answer is:

abet

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'assist' is the definition.
(abetting is a kind of assisting)

'argentina's foremost banker say' is the wordplay.
'foremost' suggests taking the first letters.
'banker say' becomes 'bet' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'argentinas' is 'a'.
'a'+'bet'='ABET'

Can you help me to learn more?

(Other definitions for abet that I've seen before include "Assist (in doing wrong?)" , "Assist criminally" , "Aid and assist" , "Encourage (offence)" , "Help a criminal" .)

I've seen this clue in The Telegraph.

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