Order to relax (2,4)
I believe the answer is:
at ease
'order to relax' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for at ease that I've seen before include "with no worries" , "Relax - that's an army order" , "Army command to relax, stand with feet apart" , "Military order to relax from attention" , "Relaxing - that's a military order" .)