This much-reduced circular feature has been considered as a possible henge. Certainly the ditch is internal to the bank. Coflein description:
A sub-oval enclosure, 132m N-S by 116m, defined originally by a bank and ditch, bisected by an E-W modern road and best preserved to the N.
CPAT website mentions eight possible henges in Montgomeryshire. This one is referred to as being at Four Crosses: