A waterfowl on the Nile (5)

I believe the answer is:

aswan

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But I can't explain it at all! Could you help me understand?

(Other definitions for aswan that I've seen before include "Egyptian city and dam" , "Ancient city on the Nile" , "Large dam in Egypt" , "Nile High Dam" , "Site of dam on the Nile" .)

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