Part of garden ruthlessly lifted up and transformed (6)
I believe the answer is:
turned
'transformed' is the definition.
(turning is a kind of transforming)
'part of garden ruthlessly lifted up' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'lifted up' says the letters should be written backwards (in a down clue, letters go up).
'denrut' is hidden within 'garden ruthlessly'.
'denrut' backwards is 'TURNED'.
'and' acts as a link.
(Other definitions for turned that I've seen before include "Red nut (anag.)" , "Capsized" , "Revolved or changed stance" , "Moved round or changed position" , "Having soured" .)