A losing scheme is a plan or strategy that fails to achieve its intended goal. The term can be used to describe a variety of situations, such as a DIET that does not lead to weight loss. In this case, the crossword solution for the term 'losing scheme' is the four-letter word 'DIET'. A DIET is a specific eating plan that is designed to help people lose weight, but it can also be a losing scheme if it does not produce the desired results.