Study one's comic carelessly (9)
I believe the answer is:
economics
'study' is the definition.
(economics is a kind of study)
'one's comic carelessly' is the wordplay.
'carelessly' is an anagram indicator.
'ones'+'comic'='onescomic'
'onescomic' with letters rearranged gives 'ECONOMICS'.
(Other definitions for economics that I've seen before include "The study of the finances of a nation" , "Study of financial management" , "Thomas Carlyle's "dismal science"" , "Branch of knowledge dealing with material resources" , "Study of the goods and services of a country" .)