Secret American manoeuvres (2,6)
I believe the answer is:
in camera
'secret' is the definition.
(legal term meaning in private, lit. 'in a chamber')
'american manoeuvres' is the wordplay.
'manoeuvres' is an anagram indicator.
'american' with letters rearranged gives 'IN CAMERA'.
(Other definitions for in camera that I've seen before include "Conducted in private" , "With public absent" , "Kept private (law)" , "Where filming takes place" , "It's not open court" .)