I note David Sellar - an ex Lord Lyon - has written about clans that
'By way of definition, it has been suggested that, ‘Clann was used to describe a patrilineal kindred the members of which descended in known steps from a named ancestor’(From David Sellar’s, ‘Clans, origin of’ in Derrick S Thomson (ed.) Companion to Gaelic Scotland Oxford 1983) This definition underlines two points believed to be true of the clan in Scotland and in Ireland: namely that the members of the true clan were related to one another through the male line, and that the eponym or name father of the clan was a historical, and not a mythical, character. '
(Page 92 David Sellar, Chapter 4 The Family, in ed. E. J. Cowan and L. Henderson A History of of Everyday Life in Medieval Scotland, 1000 to 1600, Edinburgh University Press, Edinburgh, 2011.)
In other words clans require a central, historically real, male founder to be an historic / traditional clan. Given Gunns do not have such descent - note earlier entries showing that Gunn descent from a supposed Orkney Islands founder is ridiculous (Gunn is a 'regional name' for very early - and non kindred - inhabitants of Strathnaver / Sutherland / Caithness) then on historic / academic definitions Gunns are not a clan...