Changing to a, say, breakfast porridge (7)

I believe the answer is:

oatmeal

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'porridge' is the definition.
(I know that oatmeal is a type of porridge)

'changing to a say breakfast' is the wordplay.
'changing' indicates an anagram.
'say breakfast' becomes 'meal' (I can't explain this - if you can you should believe this answer much more).
'to'+'a'='toa'
'toa' is an anagram of 'oat'.
'oat'+'meal'='OATMEAL'

Can you help me to learn more?

(Other definitions for oatmeal that I've seen before include "Breakfast dish" , "Porridge ingredient" , "Ground grain used to make porridge" , "Ground grain; colour" , "Plain food" .)

I've seen this clue in The Daily Express.

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