Concert piece that never fails (4)
I believe the answer is:
cert
'piece that never fails' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'concert' is the wordplay.
'CERT' is hidden in amongst the letters.
But, I'm unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for cert that I've seen before include "Classification" , "Infallible bet (slang)" , "Sure thing (sl.)" , "Safe bet" , "Sure thing (that could be dead!)" .)