The crossword solution for the term 'tightens, with 'UP'' is 'TENSES'. Tenses are forms of a verb that indicate when an action takes place. In English, there are three main tenses: present, past, and future. The present tense is used to describe actions that are happening now or in the near future. The past tense is used to describe actions that have already happened. The future tense is used to describe actions that will happen in the future. The term 'tightens, with 'UP'' refers to the fact that the verb form changes depending on the tense. For example, the verb 'TIGHTEN' changes to 'tightened' in the past tense and 'TIGHTENING' in the present tense.