Breakfast mix (6)
I believe the answer is:
muesli
'breakfast mix' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for muesli that I've seen before include "Breakfast mush" , "Swiss breakfast?" , "Breakfast food of cereal, nuts, dried fruit etc with milk" , "Breakfast food of cereals, dried fruit, nuts etc" , "Mixture of crushed grain, nuts etc" .)