Clan, n.
Etymology: [Gael. clann offspring, descendants; akin to Ir. clann, cland, offspring, tribe, family; perh. from L. plania scion, slip, cutting. Cf. Plant, n.]
1. A tribe or collection of families, united under a chieftain, regarded as having the same common ancestor, and bearing the same surname; as, the clan of Macdonald. "I have marshaled my clan." Campbell.
2. A clique; a sect, society, or body of persons; esp., a body of persons united by some common interest or pursuit; -- sometimes used contemptuously. Partidge and the rest of his clan may hoot me. Smolett. The whole clan of the enlightened among us. Burke.
Shades of meaning
Fernald has no entry of its own for clan; he lists it under class.
He lists it without comment; the entries above explain its neighbors.