The term 'A Necessary Thing' can be summarized as something that is essential or required. It is often used to refer to something that is necessary for a certain task or goal to be achieved. For example, a necessary thing for a successful business might be a good customer service system or a reliable source of funding. In the crossword, the solution for this term is 'MUST', which is an acronym for 'Mandatory Undertaking of Specific Tasks'. This acronym emphasizes the importance of completing certain tasks in order to achieve a desired outcome.