End Expedition is an action performed by pressing the appropriate button.
To have all clan members stop following you, stop moving and the End Expedition action will appear. Press the appropriate button and all clan members following you will stop following you. Clan members may move off a bit and begin doing other activities on their own as you no longer are asking them to follow you.
To have a single clan member stop following you, move to them and the Wait Here action will appear. Press the appropriate button and that member will stop following you.