Go off duty (5,4)
I believe the answer is:
stand down
'go off duty' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stand down that I've seen before include "Withdraw voluntarily, from job or competition" , "Leave the witness box" , "Exhibition equipment packed up" , "Relinquish one's post" , "Quit" .)