Salad ingredient, mostly green on plate (6)
I believe the answer is:
radish
'salad ingredient' is the definition.
(radishes are often used in salads)
'mostly green on plate' is the wordplay.
'mostly' means to remove the last letter.
'green' becomes 'raw' (both can mean naive or inexperienced).
'on' is a charade indicator (letters next to each other).
'plate' becomes 'dish' (type of plate).
'raw' with its final letter removed is 'ra'.
'ra'+'dish'='RADISH'
(Other definitions for radish that I've seen before include "Pungent red salad root" , "Sir had this vegetable" , "Hard vegetable" , "Edible small root" , "Daikon or mooli" .)