Crossword Genius

Source of fake news about protest (4)

Ross

I believe the answer is:

rail

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'protest' is the definition.
(I've seen this before)

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

Can you help me to learn more?

(Other definitions for rail that I've seen before include "Bar - marsh bird" , "Kind of transport" , "A bird; bar to hang on" , "Complain bitterly - wading bird" , "Bar of rolled steel" .)

I've seen this clue in The Independent.
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