Privately, American misbehaving (2,6)
I believe the answer is:
in camera
'privately' is the definition.
(I've seen this before)
'american misbehaving' is the wordplay.
'misbehaving' is an anagram indicator.
'american' is an anagram of 'IN CAMERA'.
(Other definitions for in camera that I've seen before include "With public absent" , "It's not open court" , "place for a film?" , "'In private (2,6)'" , "as films these days are less often seen" .)