Certain cereal (3)
I believe the answer is:
rye
'certain cereal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rye that I've seen before include "Type of whisky" , "Grass - whiskey" , "Cereal grain" , "Grain used in flour and whiskey" , "(Gypsy) gent; type of bread, whiskey" .)