As a native Scot living in Scotland it is my understanding of the position that although a clan or family may have no chief, the Lord Lyon can grant the right to bear Arms to individual members of that family, hence the clan or family is commonly referred to as armigerous, although it is the individual members rather than any clan chief who bear Arms.
When I had previously referred in another thread to a link to wikipedia as supporting the view that clans such as Crawford and Cunningham were armigerous, MoR was quick to contradict this and call the wiki article garbage, yet the Scottish Clan & Family Encyclopaedia by George Way of Plean and Romilly Squire which I regard as the authoritative work on such matters, lists these clans under the section headed "The Armigerous Clans and Families of Scotland"