A kid is chilled-out (2,4)
I believe the answer is:
at ease
'chilled-out' is the definition.
'a kid' is the wordplay.
'kid' becomes 'tease' (I've seen this in other clues).
'a'+'tease'='AT EASE'
'is' is the link.
(Other definitions for at ease that I've seen before include "Army command to relax, stand with feet apart" , "Free from anxiety" , "Relax - that's an army order" , "unworried" , "In a relaxed attitude" .)