"primary order" refers to the main or most important instruction or task. It is the initial or fundamental action that needs to be carried out before anything else. Full definition
Every cylinder added beyond five increases the overlap of firing strokes and makes for less primary order vibration. (en.wikipedia.org)
The only basis upon which the wife might make her application was if the amendment aided the original primary order but this was not the case and, in fact, her application would undermine the original order. (ukscblog.com)
primary order means an order under this Act affecting children and includes such order as varied. (legislation.gov.au)