A half of rice, and that's a fact (6)
I believe the answer is:
cereal
'a fact' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'a half of rice and that's' is the wordplay.
'a half of' suggests halving the letters.
'and' is a charade indicator (letters next to each other).
'that' becomes 'real' (I am not sure about this - if you are sure you should believe this answer much more).
'rice' with half the letters taken is 'ce'.
'ce'+'real'='CEREAL'
Can you help me to learn more?
(Other definitions for cereal that I've seen before include "Grass cultivated for food" , "Breakfast food made from grain" , "11 food, maybe" , "Contents of breakfast bowl" , "Grain used for food" .)