Half-cent genuine grain (6)
I believe the answer is:
cereal
'grain' is the definition.
(I know that grain can be written as cereal)
'half-cent genuine' is the wordplay.
'half' indicates taking half.
'genuine' becomes 'real' (similar in meaning).
'cent' with half the letters taken is 'ce'.
'ce'+'real'='CEREAL'
(Other definitions for cereal that I've seen before include "Rye, for example" , "11 food, maybe" , "output from harvest?" , "'Wheat or maize, say (6)'" , "Common part of breakfast" .)