Eco-friendly but inexperienced (5)
I believe the answer is:
green
I believe this clue is a double definition.
'eco-friendly' is the first definition.
(green can mean good for the environment)
'inexperienced' is the second definition.
(similar in meaning)
'but' acts as a link.
(Other definitions for green that I've seen before include "Colour of malachite" , "Caring for environment" , "Gullible" , "Envious; naive" , "Ecologically correct" .)