Probably a gravel pit, as many such pits are indicated on late C19 OS maps (although not this example).
A pit 3m diameter and 0.75m deep, grass-covered. Located in downhill angle of field boundaries (NPRN 500303 and 500314).
Recorded as part of Uplands Initiative Survey. W B Horton, Hayman and Horton, 06/06/2007.