A breakfast food (6)
I believe the answer is:
muesli
'a breakfast food' is the definition.
(I know that muesli is a type of breakfast food)
This is all the clue.
(Other definitions for muesli that I've seen before include "Swiss cereal" , "Breakfast dish with cereals, nuts, fruit etc" , "Breakfast food of cereals, fruits, nuts etc" , "Mixture of cereals etc" , "Rolled oats, nuts and fruit mixture" .)