No excuse for pleasure that's certain (4)

I believe the answer is:

sure

I'm a little stuck... Click here to teach me more about this clue!

'certain' is the definition.
(I know that certain can be written as sure)

'no excuse for pleasure' is the wordplay.
'SURE' is hidden in amongst the letters.
However, I am uncertain how the hidden word is indicated.

'that's' acts as a link.

Can you help me to learn more?

(Other definitions for sure that I've seen before include "Feeling no doubt" , "Completely certain" , "Agreed" , "Definite" , "Certain, confident" .)

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

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