The term 'Man on First' is a baseball term used to describe the position of the first baseman. The crossword solutions for this term are ADAM (4 letters) and WHO (3 letters). ADAM is likely referring to ADAM LaRoche, a former Major League Baseball first baseman who played for the Atlanta Braves, Pittsburgh Pirates, Boston Red Sox, Arizona Diamondbacks, Washington Nationals, and Chicago White Sox. WHO is likely referring to the popular phrase 'Who's on first?' which is a comedy routine made famous by the American comedy duo Abbott and Costello.