A clochaun, sometimes written clochán, is a dry-stone corbelled hut, built without mortar by layering inward-tapering stones until they meet at the top to form a beehive-shaped roof. Single examples are common across the Corca Dhuibhne peninsula, associated mostly with early Christian hermits and monks who favoured its remote western reaches. A quadruple example, four such cells joined together or grouped in close formation, is a considerably rarer thing.

The record of this structure comes from the archaeologist R. A. S. Macalister, who noted it in 1899. Macalister was one of the most prolific figures in early Irish archaeology, working across the island at a time when much field documentation was still being done for the first time. His observation that the clochaun at Fán was both large and quadruple in form places it in a small category of more complex corbelled structures, which may suggest communal rather than solitary use, though the site's precise function and date remain matters for interpretation rather than certainty.