Crowd noise is unrefined we hear (4)

I believe the answer is:

roar

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'crowd noise' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for roar that I've seen before include "Lion's call" , "Lion's noise" , "24 [BOOM]" , "Yell" , "Great cry" .)

I've seen this clue in The Sun.

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