The North Somerset Know Your Place website lists this as MNS6587, Stone 180m SE of Cannaways Farm and describes it as Post-medieval without further reference. It does mention a second to the SSW, 240m SSE of Cannaways Farm which it also laconically calls 'Post-medieval'. The HER map gives the same - but no further information.
Something is not right. This message is just to keep things from messing up down the road