Coarse crusts are genuine breakfast (6)
I believe the answer is:
cereal
'breakfast' is the definition.
(I've seen this before)
'coarse crusts are genuine' is the wordplay.
'crusts' means to remove the middle letters (I've seen 'crust' mean this (the outside or crust of the word is used)).
'are genuine' becomes 'real' (similar in meaning).
'coarse' with its centre removed is 'ce'.
'ce'+'real'='CEREAL'
(Other definitions for cereal that I've seen before include "Edible grain for breakfast" , "Eg, wheat, rye, corn" , "Grain crop" , "Starchy grains used as food" , "Grain used for food" .)