The term 'tightens, as a belt' can be summarized by the crossword solution 'girds, ' which is a five-letter word. Girding is the act of encircling or binding something with a belt or band, such as a waistband or a girdle. This term is often used to describe the action of tightening a belt around one's waist in order to make it fit more snugly. Girding is also used to describe the process of securing a rope or cable around an object in order to secure it in place.