This site is one of those ones that nobody can agree upon. The most interesting explanation is that it’s the remains of a stone circle, but it’s also been interpreted as a stone row, or just some sort of ruined megalithic structure. Here’s what N.P. Figgis says about it in Prehistoric Preseli:
A group of stones, variously considered as a pair with one stone fallen and – least likely – remnants of a circle of which most are fallen. No early reference or place names suggest the presence of a circle; the three stones involved would indicate an enormous diameter. Interpretation open to suggestions!
I agree with Figgis that the circle would be whopping if that’s what it was. Based on what I’ve seen I reckon it’s a stone row.