It's used in fixing no mean garden ornament (5)
I believe the answer is:
gnome
'garden ornament' is the definition.
(I've seen this in another clue)
'it's used in fixing no mean' is the wordplay.
'it's used in' indicates a hidden word.
'GNOME' is hidden in the letters of 'fixing no mean'.
(Other definitions for gnome that I've seen before include "Saw" , "Creature in garden (or Zurich?)" , "Mythical sprite" , "Legendary being (from Zurich)?" , "Zurich financier" .)