Crazy mount rearing following quiet procedure (8)

I believe the answer is:

protocol

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

I cannot understand how the remainder of the clue works.

(Other definitions for protocol that I've seen before include "customs" , "Diplomatic rules" , "Procedural rules" , "Diplomatic etiquette or procedure" , "Poor clot involved in kind of status etiquette" .)

I've seen this clue in The Guardian.

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