This is the 4603rd most frequent German word.
sportliche
"Sportliche" means "sporty" or "athletic" in English.
Here, "sportliche" is used as an adjective describing "Leistung" (performance), indicating it's related to sports.
Ich bewundere ihre sportliche Leistung.
I admire her athletic performance.
In this context, "sportliches" modifies "Verhalten" (behavior) to convey the idea of a fair and active attitude related to sports.
Durch sein sportliches Verhalten zeigte er Fairness.
Through his sporty behavior, he showed fairness.
Here, "sportliche" describes "Mitglieder" (members), implying they should be athletic and involved in sports.