Undeniable muddle as Nile disappears into another river? (6)

I believe the answer is:

danube

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'river?' is the definition.
(Danube is an example)

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

(Other definitions for danube that I've seen before include "River flowing from Black Forest to Black Sea" , "River in Europe" , "Viennese river" , "flower" , "Major European river" .)

I've seen this clue in The Irish Times.

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