Breakfast or dinner (4)
I believe the answer is:
meal
This clue is a double definition.
'breakfast' is the first definition.
(thesaurus)
'dinner' is the second definition.
(dinner is a meal)
(Other definitions for meal that I've seen before include "Eg, breakfast" , "Scoff" , "Something to eat" , "Meat and two veg plus dessert, perhaps" , "Repast" .)