Smacking a fly is an action that involves using one's hand to quickly hit a fly in order to kill it. The term 'smack a fly' is often used as a metaphor for taking quick and decisive action. In this crossword, the solution for the term 'smack a fly' is SWAT, which stands for Special Weapons and Tactics. SWAT teams are specialized police units that are trained to respond quickly and decisively to dangerous situations.