Half of ragu on plate is a vegetable (6)
I believe the answer is:
radish
'vegetable' is the definition.
(radish is a type of vegetable)
'half of ragu on plate' is the wordplay.
'half of' indicates taking half.
'on' says to put letters next to each other.
'plate' becomes 'dish' (type of plate).
'ragu' cut in half is 'ra'.
'ra'+'dish'='RADISH'
'is a' acts as a link.
(Other definitions for radish that I've seen before include "Bit of salad" , "Daikon or mooli" , "Small red salad vegetable" , "Hottish salad plant" , "Pungent fleshy edible root eaten in salads" .)