Wise person keeping feature of Glastonbury in preservation (7)
I believe the answer is:
storage
'preservation' is the definition.
(thesaurus)
'wise person keeping feature of glastonbury' is the wordplay.
'wise person' becomes 'sage' (sage can mean a wise or holy person).
'keeping' indicates putting letters inside.
'feature of glastonbury' becomes 'tor' (Glastonbury Tor in Somerset).
'sage' going around 'tor' is 'STORAGE'.
'in' is the link.
(Other definitions for storage that I've seen before include "Depository space for goods" , "reservation?" , "Cost of keeping in a warehouse" , "Longer-term laying up" , "safekeeping" .)