Growing your clan is important, but not all members are equal. In order to succeed, you should make sure that everyone in your group is contributing by earning Clan Points. There are two tools inside your Clan Settings (open your clan and tap your clan photo) that can help with this:

Private Clans
You may want to be a bit more selective about membership in your growing clan. Set your clan to private by unchecking 'Open to anyone', and players will need to request to join your clan. As clan leader, you can approve or reject join requests from the Notifications tab.

Clans are 'Open to anyone' by default, but this setting can be changed at any time.

Remove Inactive Users
With this setting enabled, your clan will automatically kick users who have not logged in within a certain number of days, which you can specify using the slider shown. This will ensure that spots in your clan are free for people who actively play and can help your clan!