The clown is a minor character in "Othello." He is a jester, or fool. The clown jokes lewdly with the musicians in Act III scene 1 before dismissing them with Othello's payment. In Act III scene 4 he briefly jests with Desdemona before carrying a message for her.
As comic relief, the clown does not do much to interrupt the play's increasing tension; he may just serve as a conventional character expected by Shakespeare's audiences and therefore aptly supplied to please the masses.