Part of salad not left on a plate (6)
I believe the answer is:
radish
'part of salad' is the definition.
'not left on a plate' is the wordplay.
'not left' becomes 'r' (abbreviation for right).
'on' is a charade indicator (letters next to each other).
'plate' becomes 'dish' (I've seen this before**).
'r'+'a'+'dish'='RADISH'
(Other definitions for radish that I've seen before include "Sir had this vegetable" , "Daikon or mooli" , "Red cold salad ingredient" , "Root eaten raw in salads" , "Edible small root" .)