Yes, an admin user with manage workspace permissions can remove a workspace by following these instructions:
Click the dropdown arrow at the top left corner of your Wealthbox screen beside the current workspace name to navigate to the "Manage Workspaces" page in Settings.
From the Manage Workspaces page you will see a "Delete" option to the right of each workspace. This will remove the workspace from your workspace dropdown list along and will also remove access for all users.