Exec's order (4)
I believe the answer is:
asap
'exec's order' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for asap that I've seen before include "yesterday?" , "'As quickly as you can, initially (4)'" , "Notation for as quickly as you can" , "As soon as possible (abbrev.)" , "Notation for urgent, quick as you can (4)" .)