As you follow the path past the trig pillar, you can just about make out the enclosure, the cairn and the RA are about 10m to the left of the path, where the land starts to slope down again, and the bracken starts to give way to heather.
This one’s actually a bit easier to find in summer, as the bracken doesn’t grow on the cairn, making the barer patch easier to spot.
Note that the paths marked on the OS map bear only a vague resemblance to the paths visible on the ground, largely due to bracken infestation.