No. It must be real. Otherwise you couldn’t honestly answer the question.
You may think free will is an illusion, but if an antecedent action, event or power external to your consciousness ultimately caused or determined that thought for you, then how do you know if you’re right or not?
Free will is the power to consciously choose between alternatives. Existence or nonexistence? True or false? Right or wrong? These are alternatives, too.
Anyone who says they believe free will is an illusion is contradicting their own claim. In order to deny the existence of free will, you must rely on its power. You must believe in it.