Great stream of effortless industry (5)

I believe the answer is:

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'great stream' is the definition.
'Indus' can be an answer for 'stream' (Indus is an example). I am not certain of the 'great' bit.

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

Can you help me to learn more?

(Other definitions for indus that I've seen before include "Pakistani river" , "Major Asian river" , "Sacred flower" , "Long Asian river" , "Asian runner" .)

I've seen this clue in the Evening Standard.

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