The term 'UNDO A LEAD' can be summarized as the act of removing a lead, which is a type of metal that is used in construction and other industries. The crossword solution for this term is 'TIE', which refers to the process of tying the lead together in order to secure it in place. This process is often used when installing lead-based materials, such as roofing or siding. Once the lead is secured, it can then be removed by untying the ties.