Without a care in the world for Smiley (6)
I believe the answer is:
jovial
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for jovial that I've seen before include "Convivial" , "Good-humoured, cheerful" , "Hearty and cheerful like Jupiter" , "Genial, joyous" , "Happy and cheerful" .)