When we don't grasp a concept or idea clearly, we may use the phrase "be unclear about/as to something". However, there are many other synonyms that can be used to express this lack of understanding. For instance, one can say they are "confused", "uncertain", or "perplexed" about a topic. Another option is to say they are "unsure" or "ambiguous" regarding the matter. Additionally, one may use the phrase "don't have a clear understanding" or "have a hazy perception" to describe their state of confusion. Overall, there are many ways to express confusion and lack of clarity of something, which can help in effective communication.