The term 'trooper leader' refers to a military officer who is in charge of a unit of troops. The crossword solution for this term is 'PARA', which is an abbreviation for Paratrooper, a type of soldier who is trained to parachute from aircraft and land behind enemy lines. Paratroopers are highly trained and skilled soldiers who are capable of carrying out difficult missions. They are usually led by a trooper leader, who is responsible for the safety and success of the mission.