The crossword solution for the term 'Historical Topic' is 'ERA'. An ERA is a period of time in history that is defined by certain characteristics or events. It is usually used to refer to a long period of time, such as the Middle Ages or the Industrial Revolution. It can also refer to a shorter period of time, such as the Roaring Twenties or the Age of Enlightenment. An ERA can be used to divide up history into more manageable chunks, making it easier to study and understand.