The term 'PAY UP' can be broken down into four crossword solutions: PONY (4 letters), SETTLE (6 letters), ANTE (4 letters), and REMIT (5 letters). PONY is a small horse, and to SETTLE is to come to an agreement or resolution. ANTE is a stake or contribution made in a game, and REMIT is to send money or payment. Together, these words suggest that someone is being asked to pay up, or make a payment, in order to SETTLE a debt or game.