Relaxed, unconcerned (6)
I believe the answer is:
casual
I believe this is a double definition.
'relaxed' is the first definition.
(I've seen this before)
'unconcerned' is the second definition.
(similar in meaning)
(Other definitions for casual that I've seen before include "Insouciant" , "Relaxed - unintentional" , "Informal or easygoing" , "displaying lack of commitment" , "Careless, without serious commitment" .)