선수단 = 선수 (Player) + 단(Group, team)
기자단 =기자( reporter, journalist, press) + 단(group)
탐사단 = 탐사(exploration) + 단(group, team)
It's more like squad as it has military connotations. A group or team facing some danger or difficulty together, like a cheer-leading squad. It's used in names of bands too, as in that "Bulletproof Youth Squad", but . . .