Daffy coming from the deep to bowl over (4)

I believe the answer is:

stun

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

I can't explain the remainder of the clue.

(Other definitions for stun that I've seen before include "Daze, overwhelm" , "deliver a knock-out blow" , "Confound" , "Shock into silence" , "Leave speechless" .)

I've seen this clue in The Telegraph.

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