The term 'timeline CHAPTER' is composed of two words: 'timeline' and 'CHAPTER'. A timeline is a visual representation of events in chronological order, often used to illustrate the history of a particular subject. A CHAPTER is a section of a book or other written work, usually dealing with a particular topic. Therefore, a timeline CHAPTER is a section of a book or other written work that focuses on a particular timeline. The crossword solution for the term 'timeline CHAPTER' is 'ERA', which refers to a period of time in history.