The term 'clear-thinking' can be defined by four crossword solutions: LOGIC, LUCID, SOBER, and SANE. LOGIC is the process of reasoning in a systematic way, while LUCID means to be clear and easily understood. Sobriety is the state of being SOBER, or not under the influence of drugs or alcohol, and SANE is the state of being mentally sound. Together, these four words describe the concept of clear-thinking, which is the ability to think rationally and make sound decisions.