Quit flipping urns! (4)

I believe the answer is:

stop

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'quit' is the definition.
(I know that quit can be written as stop)

I don't understand the remainder of the clue.

(Other definitions for stop that I've seen before include "Organ knob; get bus here" , "Cease, halt" , "Withhold large amount raised" , "Hold on" , "It could be the organist's principal" .)

I've seen this clue in the Sydney Morning Herald.

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