Three stripped - feature of Glastonbury? (3)
I believe the answer is:
tor
'feature of glastonbury?' is the definition.
(Glastonbury Tor in Somerset)
I don't understand the remainder of the clue.
(Other definitions for tor that I've seen before include "High, rocky, bare hill" , "Rot on a hill in Devon" , "Rocky height, eg Mam" , "Rot on a Cornish hill" , "Rot about the rocky height" .)