What successful European banks (3)

I believe the answer is:

leu

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'what successful european banks' is the definition.
I can't judge whether this definition defines the answer.

'what successful european banks' is the wordplay.
'LEU' is hidden in amongst the letters.
However, I'm not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for leu that I've seen before include "Money" , "Currency" , "In E Europe, change" .)

I've seen this clue in The Independent.

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