It's alarming, Oscar losing his head and coming to a sticky end! (5)

I believe the answer is:

scary

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'it's alarming' is the definition.
(similar in meaning)

I can't explain the remainder of the clue.

(Other definitions for scary that I've seen before include "[SPICE]" , "spook" , "Frightening or spooky" , "Hair-raising" , "Fearsome" .)

I've seen this clue in the Evening Standard.

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