Breakfast foods (7)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">breakfast foods</span>' is the definition.<br/ ><span class="explanation-format__explanation">(cereal is a kind of breakfast food)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for cereals that I've seen before include "Foods such as rye, wheat, etc" , "Stubbornly unmoving" , "Breakfast foods" , "Starchy grains used as food" , "Grain foods" .)