Breakfast food, originally developed by a Swiss doctor for his patients (6)
I believe the answer is:
muesli
(Other definitions for muesli that I've seen before include "Breakfast dish of cereal, dried fruit and nuts in milk" , "Mixture of grain and dried fruit" , "Cereal made with oats and nuts" , "eaten at breakfast" , "Breakfast mix of oats, nuts, fruit etc" .)