A blank shot from this cruiser signalled the attack on the Winter Palace which started Russia's October Revolution (6)

I believe the answer is:

aurora

(Other definitions for aurora that I've seen before include "7 ... borealis, ... lights" , "Northern/southern lights" , "Dawn, Sleeping Princess" , "Phenomenon in sky" , "Gentle breeze for goodess of Dawn" .)

I've seen this clue in The Times.

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