Porridge-maker beginning to overeat at breakfast? (7)
I believe the answer is:
oatmeal
'porridge-maker' is the definition.
'beginning to overeat at breakfast?' is the wordplay.
'beginning to' says to take the initial letters.
'breakfast?' becomes 'meal' (breakfast is a kind of meal).
The first letter of 'overeat' is 'o'.
'o'+'at'+'meal'='OATMEAL'
(Other definitions for oatmeal that I've seen before include "Kind of porridge" , "Basis of porridge" , "Greyish-fawn colour flecked with brown" , "Pale variegated brown colour" , "Eat loam (anag)" .)