Clans can have up to 50 players, with members organized into 4 earned ranks.  After tapping  on a Clan Mate's info screen, you'll be given various actionable options per your rank.

For example, this is what the Clan Leader sees when he taps on a Co-leader's name:

The responsibilities that each rank can control are:

Member

When you join or re-join a clan, you will automatically earn membership. Even  if you were an Elder, Co-Leader or Leader in another or the same clan before, when you join a clan you will alway