The term 'PREPARE TO SCORE ON A SAC FLY' is a baseball term. It means that the batter is preparing to score a run on a sacrifice fly, which is when a batter hits a fly ball that allows a runner on base to score. The crossword solution for this term is TAGUP, which is a baseball term meaning that a runner on base is tagging up, or getting ready to run, in anticipation of a fly ball being hit.