Early start. Cereal box empty. Disastrous. Awful (9)
I believe the answer is:
execrable
'awful' is the definition.
(thesaurus)
'early start cereal box empty disastrous' is the wordplay.
'start' says to take the initial letters.
'empty' says to hollow out the word (remove centre letters).
'disastrous' indicates anagramming the letters.
'box' with its middle removed is 'bx'.
The initial letter of 'early' is 'e'.
'cereal'+'bx'='cerealbx'
'cerealbx' anagrammed gives 'xecrable'.
'e'+'xecrable'='EXECRABLE'
(Other definitions for execrable that I've seen before include "Loathsome" , "Woeful" , "Appalling, abhorrent" , "Extremely bad or unpleasant" , "Dreadful" .)