The circus performers were actually criminals and sold poor trusting Zukki-dar into slavery where he toils sadly on a Dunmer plantation hoping the sudden cessation of letters to his patron will warrant a search party. Unfortunately, the circus performers have been forging the same letter over and over again to make you think poor Zukki-dar has indulged too much in the Skooma. As long as they send you a few cheap and probably nearly spoiled circus rations along with the letter, you'll never suspect a thing.

there's a traveling troupe near the bottom of Grahtwood.
Did the quest years ago.
Had to help find some of there performers.

Circus in Rome was where chariot racing and games were held I.e circus maximus was I think the largest in the empire. By that definition VMA and DSA are a circus of sorts.so some people heading that way would be circus performers.
Then you have circus skills as opposed to a conventional circus such as poi, diablo, trapeze, juggling among others. So then anyone with a fire breathing, knife juggling, sword swallowing emote could be a circus performer when displaying the skills.
However sometimes in area chat you find the biggest clowns putting on a show for the masses just maybe Zukki can read area chat.