Breakfast mixture (6)
I believe the answer is:
muesli
'breakfast mixture' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for muesli that I've seen before include "Breakfast food of cereal, nuts, dried fruit etc with milk" , "Breakfast food of cereals, dried fruit, nuts etc" , "Swiss breakfast?" , "Granola-like food" , "Mule is fed with breakfast compound" .)