A kid with feet up, perhaps (2,4)
I believe the answer is:
at ease
'feet up perhaps' is the definition.
I can't tell whether this definition defines the answer.
'a kid' is the wordplay.
'kid' becomes 'tease' (both can mean to mock).
'a'+'tease'='AT EASE'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for at ease that I've seen before include "Free from anxiety" , "Army command to relax, stand with feet apart" , "Relaxed, not tense - that's an order" , "Relaxing - that's a military order" , "resting" .)