Dish is missing when not there (4)
I believe the answer is:
tray
'dish' is the definition.
(thesaurus)
'missing when not there' is the wordplay.
'missing' becomes 'astray' (something that's gone astray is missing).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'not there' is a deletion indicator.
'astray' with 'as' taken away is 'TRAY'.
'is' acts as a link.
(Other definitions for tray that I've seen before include "three" , "Domestic carrier" , "Flat utensil for carrying meal" , "Shallow receptable for carrying something" , "food container" .)