Antonyms for the phrase 'have a handle on' refer to the lack of control, knowledge or understanding. Words that denote control can include mismanage, bungle, mishandle, overlook, or neglect. When it comes to the absence of knowledge or understanding, antonyms such as clueless, unaware, uninformed, or ignorant could be used. By contrast, words that indicate a lack of authority or power can include helpless, powerless, or ineffectual. In situations where one doesn't have the required skills or expertise, unskilled or inexperienced can be used as antonyms. These words can help describe situations where one is trying to establish a sense of control and providing a clearer understanding of what is not known.