Intellectual bore oddly covered in breakfast food (8)
I believe the answer is:
cerebral
'intellectual' is the definition.
('cerebral' can be a synonym of 'intellectual')
'bore oddly covered in breakfast food' is the wordplay.
'oddly' means one should take alternating letters.
'covered in' is an insertion indicator.
'breakfast food' becomes 'cereal' (cereal is a kind of breakfast food).
The alternating letters of 'bore' are 'br'.
'br' put inside 'cereal' is 'CEREBRAL'.
(Other definitions for cerebral that I've seen before include "Highly intellectual" , "Relating to the brain" , "Concerning the brain" , "Of the brain, intellectual" , "Intellectual, brainy" .)