Terrible meal in tray is nourishing (10)
I believe the answer is:
alimentary
'is nourishing' is the definition.
(thesaurus)
'terrible meal in tray' is the wordplay.
'terrible' indicates anagramming the letters.
'meal'+'in'+'tray'='mealintray'
'mealintray' with letters rearranged gives 'ALIMENTARY'.
(Other definitions for alimentary that I've seen before include "of food" , "providing nourishment" .)