totally uninformed about what is going on; not having even a clue from which to infer what is occurring
"After three hours of staring at the confusing instructions without asking anyone for help, I realized that my new roommate was completely clueless about how to operate the coffee machine."
Lacking knowledge or understanding; uninformed; oblivious.
"The new intern was completely clueless about the company's internal software, so I had to walk him through every single step manually."