Edict on new grass (4)
I believe the answer is:
lawn
'grass' is the definition.
(a lawn is an area of grass)
'edict on new' is the wordplay.
'edict' becomes 'law' (I've seen this before).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'new' becomes 'n' (abbreviation as in New Testament NT).
'law'+'n'='LAWN'
(Other definitions for lawn that I've seen before include "Area of short grass" , "Cultivated and mowed grass" , "Fine fabric" , "Fine cotton or grass garden" , "Area of tended grass" .)