Crossword Genius

Sinful centre for troubadours (3)

Ross

I believe the answer is:

bad

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

Here is my best explanation:

'sinful' is the definition.
(thesaurus)

'centre for troubadours' is the wordplay.
'BAD' is hidden within the letters.
However, I am not sure how the hidden word is indicated.

Can you help me to learn more?