Sloppy cereal unsettled sons (8)
I believe the answer is:
careless
'sloppy' is the definition.
('careless' can be similar in meaning to 'sloppy')
'cereal unsettled sons' is the wordplay.
'unsettled' indicates anagramming the letters.
'sons' becomes 'ss' (I've seen this in other clues).
'cereal' anagrammed gives 'carele'.
'carele'+'ss'='CARELESS'
(Other definitions for careless that I've seen before include "Inconsiderate" , "Unconcerned; casual" , "Lax" , "Unthinking and irresponsible" , "'Thoughtless, inattentive (8)'" .)