Cursory or informal (6)
I believe the answer is:
casual
I believe this clue is a double definition.
'cursory' is the first definition.
(I know that cursory can be written as casual)
'informal' is the second definition.
(similar in meaning)
(Other definitions for casual that I've seen before include "Informal or blase" , "Not concerned" , "Informal or cursory" , "Informal or not showing any enthusiasm" , "Informal, not methodical" .)