Boiled oatmeal (8)
I believe the answer is:
porridge
'boiled oatmeal' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for porridge that I've seen before include "type of bird" , "Breakfast dish - spell in prison" , "Morning oats" , "Possibly breakfast - time in prison" , "milk and oats together" .)