Break without warning (4)

I believe the answer is:

snap

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'break' is the definition.
(I know that snap is a type of break)

I can't explain the rest of the clue.

(Other definitions for snap that I've seen before include "Break; liveliness" , "Short spell" , "Break like simple card game" , "unexpected? > Same here!" , "Break - children's card game" .)

I've seen this clue in The Globe and Mail.

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