More colourful, environmentally (7)
I believe the answer is:
greener
'more colourful' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for greener that I've seen before include "More environmentally sensitive" , "More gullible" , "better for the environment" , "The grass is always thus on the other side of the hill" , "more colourful" .)