There are several synonyms for the phrase "have no idea" that you can use in your writing or conversation to express your uncertainty or lack of knowledge. Some alternatives include "clueless," "ignorant," "unsure," "in the dark," "blank," "bewildered," "perplexed," "confused," and "unclear." These synonyms allow you to communicate more effectively and accurately convey your thoughts and feelings. Whether you're trying to tell someone that you're unsure about a topic or simply don't know the answer to a question, using these synonyms can help you express yourself clearly and effectively.