The term 'INSTRUCT' (to do something) can be summarized by the crossword solution 'ENJOIN', which is a six-letter word. ENJOIN is a verb that means to order or command someone to do something, often in a formal or authoritative manner. It is derived from the Latin word 'injungo', which means to impose or lay upon. In legal contexts, ENJOIN is used to refer to a court order that requires someone to do or not do something.