Church study reduced large contribution to Harvest Festival? (6)

I believe the answer is:

cereal

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'contribution to harvest festival?' is the definition.
I can't judge whether this definition defines the answer.

'church study reduced large' is the wordplay.
'church' becomes 'CE' (Church of England).
'study' becomes 'read' (synonyms).
'reduced' means to remove the last letter.
'large' becomes 'L' (eg in clothes sizes).
'read' with its final letter removed is 'rea'.
'ce'+'rea'+'l'='CEREAL'

Can you help me to learn more?

(Other definitions for cereal that I've seen before include "Maize, rye or the like" , "Something for brekkie" , "Grass cultivated for food" , "Relating to grain" , "Breakfast food made from grain" .)

I've seen this clue in The Independent.

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