Pure corn - but sounds as if it might run (6)
I believe the answer is:
cereal
'pure corn' is the definition.
'cereal' can be an answer for 'corn' (thesaurus). I am not sure about the 'pure' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cereal that I've seen before include "Grass cultivated for food" , "Food prepared from grain" , "Breakfast food made from grain" , "Maize, rye or the like" , "Grain used for food" .)