As a concert piece, it can't fail! (4)

I believe the answer is:

cert

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'it can't fail' is the definition.
The definition suggests a singular noun which matches the answer.

'as a concert piece' is the wordplay.
'CERT' is hidden within the letters.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for cert that I've seen before include "Classification" , "Inevitable event" , "One sure to win (slang)" , "Sure thing (that could be dead!)" , "Sure thing, in short" .)

I've seen this clue in the Evening Standard.

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