Being as the crest is surrounded by a buckle, it is a clansman's badge displayed. This design can be used by any clansman. The Armiger would use the crest without surrounding it with a belt/buckle/circlet.
There is a "Clan Adair" listed as existing. The head in the center of the design of clansman's badges is the generally the Crest of the Chief. There is no Chief for Clan Adair. Apparently, technically, Adair is an Armigerous Family of Scotland. (rather than an actual clan)
Look to pages 348 -349 of the Scottish Clan and Family Encyclopedia.
The principal families recorded in the registers of the Lyon Court are those of Kinhilt and Genoch. Sir Robert Shafto Adair descended from the house of Kinhilt and was created a baronet on 2 August 1838 and his son was raised to the peerage as Baron Waveney of South Elmham, Sufolk. The peerage became extinct but the baronetcy devolved upon a younger brother, whose line continues to this day.