Cloistered (8)
'cloistered' is the definition.
(I know that cloistered can be written as secluded)
This is all the clue.
(Other definitions for secluded that I've seen before include "Quiet and private" , "Screened or sheltered from view" , "Private - withdrawn" , "Sheltered - isolated" , "Out of sight - away from society" .)
(Other definitions for monastic that I've seen before include "following order" , "Withdrawn" , "Isolated" , "Austere" , "Brother's" .)