Need to transform garden (4)
I believe the answer is:
eden
'garden' is the definition.
(Garden of Eden in the Bible)
'need to transform' is the wordplay.
'to transform' is an anagram indicator.
'need' with letters rearranged gives 'EDEN'.
(Other definitions for eden that I've seen before include "Former British PM - unspoilt paradise" , "River - garden" , "Old Testament garden" , "Paradisal garden" , "Biblical garden" .)