association
團 centers on a group of people or things gathered into a unified whole: an association, a body, or a mass. The idea is of something round or enclosed that brings parts together.
團 combines 囗 (enclosure) with 專, which likely contributes the sound and the idea of something concentrated or specialized. Together they suggest a group enclosed or gathered into a round mass.
The outer 囗 is like a fence or boundary, and inside is 專, which looks like a specialized tool or a focused hand. Picture a group of specialists gathered inside a round enclosure, forming an association.
For ダン, imagine a group of people forming a circle and chanting 'dan' together, like a round dance: dan -> ダン, and the enclosure 囗 keeps them united.
Umbonium giganteum (species of sea snail)