Less green (5)
I believe the answer is:
riper
'less green' is the definition.
('ripe' can be the opposite of 'green' so perhaps 'riper' is reasonable for 'less green')
This is all the clue.
(Other definitions for riper that I've seen before include "(Of fruit) more mature" , "like a better mousetrap?" , "More mature and ready to be eaten" , "Maturer" , "On the way to getting mellow" .)