The term 'ERA, FOR ONE' can be solved by the four letter word 'STAT'. A STAT is a statistic, which is a numerical representation of a certain event or phenomenon. Stats are used to measure and compare different aspects of a given situation, such as the performance of a team or player in a sport, or the success of a business. Stats are also used to track trends over time, such as changes in the economy or the environment. In this context, an era is a period of time in which certain stats are tracked and compared, such as the era of a particular president or the era of a particular sports team.