In the morning, cook, in case I forget (8)
I believe the answer is:
amnesiac
'i forget' is the definition.
(someone who forgets things)
'in the morning cook in case' is the wordplay.
'in the morning' becomes 'am' (AM on a clock).
'cook' indicates anagramming the letters.
'in'+'case'='incase'
'incase' anagrammed gives 'nesiac'.
'am'+'nesiac'='AMNESIAC'
(Other definitions for amnesiac that I've seen before include "I forget" , "One quite forgets" , "Forgetful person" , "Can't recall" , "Memory-loss sufferer" .)