The crossword solutions for the term BRUSH (UP) are BONE (4 letters). The phrase 'brush up' is a common idiom that means to review or practice something in order to improve one's skills. It can be used in many contexts, such as brushing up on a language or brushing up on a certain topic. The word 'BONE' is often used as a verb to mean to study or practice something diligently. Therefore, the crossword solutions for the term BRUSH (UP) could be interpreted to mean to review or practice something in order to improve one's skills.