Not as difficult (6)
I believe the answer is:
easier
'not as difficult' is the definition.
('easy' can be the opposite of 'difficult' so perhaps 'easier' is reasonable for 'not as difficult')
This is all the clue.
(Other definitions for easier that I've seen before include "More simple" , "More facile" , "Requiring less effort" , "Less complicated" , "more like a piece of cake" .)