Well done finding Mexican river (5)

I believe the answer is:

bravo

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'well done' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for bravo that I've seen before include "Thug, hired assassin; B (in radio communication)" , "Expression of approval" , "bully" , "Cry of approval" , "Radio code word for B" .)

I've seen this clue in The Sun.

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