Emerald's color (5)
I believe the answer is:
green
'emerald's color' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for green that I've seen before include "Eg, avocado, emerald" , "It's for putting on - colour - inexperienced" , "Environment-friendly" , "Area around a golf hole" , "The colour of envy" .)