A guard is either a person or an organisation. It may be a person who looks after the safety of people or property, and/or make sure prisoners do not escape. It may also be a part of the military. It can also be an object, a fireguard for example.
... of the Hegelian school, he, in company with Michelet and others, formed the "centre," midway between Erdmann and Gabler on the one hand, and the "extreme left" represented ...