Scoffing second cereal, almost replete (8)
I believe the answer is:
scornful
'scoffing' is the definition.
(thesaurus)
'second cereal almost replete' is the wordplay.
'second' becomes 's' (common abbreviation).
'cereal' becomes 'corn' (corn is a kind of cereal**).
'almost' means to remove the last letter (most of the word but not all of it).
'replete' becomes 'full' ('full' can be a synonym of 'replete').
'full' with its last letter removed is 'ful'.
's'+'corn'+'ful'='SCORNFUL'
(Other definitions for scornful that I've seen before include "Showing contempt for" , "Mocking" , "Expressing extreme contempt" , "Contemptuous or derisive" , "Openly contemptuous" .)