leader of a cheering group; head cheerleader
Refers to the person who leads a cheering squad, often in school sports or events. Can be used for both formal cheerleading teams and informal cheering groups.
As the head cheerleader, he energized the team.
The cheerleading leader's call united the audience.
応援団 is the cheering group itself, while 応援団長 is the leader of that group.
チアリーダー refers to a cheerleader in a Western-style cheerleading squad, while 応援団長 is the leader of a Japanese-style cheering group, often with a more formal or traditional role.
Compound of 応援 (cheering, support) + 団 (group) + 長 (leader). The term is straightforward and modern.