Quit flipping urns! (4)
I believe the answer is:
'quit' is the definition.
(I know that quit can be written as stop)
I don't understand the remainder of the clue.
Can you help me to learn more?
(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" .)