It’s awful when the ace turns up (3)

I believe the answer is:

bad

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

I cannot understand how the remainder of the clue works.

(Other definitions for bad that I've seen before include "Stinking" , "(Of food) decayed" , "not healthy" , "Of poor quality" , "Ill" .)

I've seen this clue in the Evening Standard.

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