Usually brownish, it's connected with green and yellow (5)
I believe the answer is:
earth
'yellow' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for earth that I've seen before include "Mud" , "Huge cost" , "Soil; ground terminal" , "Meek's inheritance" , "underground shelter" .)