You are able to delete a custom community by selecting the gear icon to the right of the custom community name.
When you select the gear, options on how to edit a community
This gives you the ability to add or remove coaches to the community.
This gives you the ability to add or remove clients to the community
This gives you the ability to rename the community. This works for the 'general' community and any custom communities.
This will remove the community. Once you delete it, it cannot be recovered. You can only delete custom communities.
This option gives the ability to hide a community that you are currently not using.