iCloud: Delete a group or a contact from a group
You can delete a group or a contact within a group at any time. You can’t delete the default All Contacts group.
Delete a group
Select the group you want to delete, then press the Delete key.
Deleting a group doesn’t delete the contacts it contains.
Delete a contact from a group
Select the group that contains the contact you want to delete.
Select the contact, then press the Delete key.
Deleting a contact from a group removes it from that group only.