River where Mississippi is crossing delta (5)

I believe the answer is:

indus

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'river' is the definition.
(Indian river)

I cannot understand how the remainder of the clue works.

(Other definitions for indus that I've seen before include "Long Asian river" , "Major Asian river" , "Important river" , "River of India and Pakistan" , "River of Southern Asia" .)

I've seen this clue in The Times.

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