A roughly circular enclosure, around forty metres across, was recorded on the third edition of the Ordnance Survey six-inch map in 1934, but no visible trace of it remains at ground level today. The land has been so thoroughly worked and levelled over the decades that whatever earthwork or boundary once defined this space has been entirely absorbed into the field.

Circular enclosures of this kind are among the most common monument types in the Irish landscape. They typically functioned as enclosed farmsteads or settlement sites, most often associated with the early medieval period, though some examples are older. The defining feature, a raised circular bank sometimes accompanied by a fosse or ditch, gave the interior a degree of shelter and demarcation. At Cluain Leannáin, that form was still legible to the mapmakers of the 1930s, even if only faintly. What makes the site quietly curious is the company it keeps: a second enclosure lies roughly twenty metres to the north-east, suggesting that this was once a more complex or at least more populated corner of the townland than its current appearance would imply. Paired or clustered enclosures occasionally indicate successive phases of settlement, or the proximity of related households, though without excavation it is impossible to say more about the relationship between the two.