Actual component of cereals (4)
I believe the answer is:
real
'actual' is the definition.
(I know that actual can be written as real)
'component of cereals' is the wordplay.
'component of' says the answer is hidden in the clue (I've seen this in other clues).
'REAL' can be found hidden inside 'cereals'.
(Other definitions for real that I've seen before include "Actual, concrete" , "Actual, not imagined" , "'Genuine, actual (4)'" , "Actual, not imaginary" , "Genuine - old Spanish coin" .)