Garden forms part of protected environment (4)
I believe the answer is:
eden
'garden' is the definition.
(Garden of Eden in the Bible)
'part of protected environment' is the wordplay.
'part of' indicates a hidden word.
'EDEN' is hidden within 'protected environment'.
'forms' acts as a link.
(Other definitions for eden that I've seen before include "In need of a great garden" , "Adam and Eve's garden" , "PM, 1955-57" , "Biblical garden" , "Tory Prime Minister, 1955-57" .)