The crossword solution for the term 'Makes Less Effective' is 'Impairs'. Impairment is a decrease in the effectiveness of something, usually caused by damage or deterioration. It can refer to physical objects, such as machines, or to abstract concepts, such as mental health. Impairment can also refer to the loss of a skill or ability due to age or illness. Impairment can have a significant impact on a person's quality of life, and can lead to disability.