The limit of your clan’s territory is defined by its border. It is dynamic and varies with time. Border limits depend on the border’s current level, which, in turn, is measured by the amount of help points accumulated. Help points are consumed every second in order to maintain the current border level. You can see the amount of help points needed to upgrade your border level, as well as consumption rates and the corresponding territory yield in your Capital’s “Border” tab.
Note that the game automatically grants you 30K help points upon the completion of clan Capital construction. If this amount drops below 20K, your territory radius will become zero and you will lose all of the possibilities that the Capital would grant you otherwise.