If your sentence is "Michael Jordan, the basketball player, won six championships for the Chicago Bulls," then the correct answer is a nonrestrictive phrase.
First of all, the underlined element cannot be a clause because there is no verb there, meaning that it has to be a phrase. Second of all, it cannot be restrictive because its meaning is not essential in this sentence - if you omitted this phrase, the sentence would still keep its meaning because everybody knows who Michael Jordan is. Thus, the correct answer is a nonrestrictive phrase.