The term 'CERTAIN BUY-IN' is a phrase used in the context of gambling, and it refers to an amount of money that must be paid by each player BEFORE a game can begin. The crossword solution for this term is 'ANTE, ' which is a Latin word meaning 'BEFORE.' This term is used in many card games, such as poker, where each player must put a certain amount of money into the pot BEFORE the game begins. This money is known as the ante, and it serves as a way to ensure that all players are invested in the game.