Final answer:
A 'warning order' in a military fire mission is a preparatory command that alerts personnel and clears communication channels for the transmission of critical targeting information.
Step-by-step explanation:
The term 'warning order' in the context of a fire mission relates to military science and communications within a military operation. Specifically, it involves the preparatory commands issued to alert personnel that a fire mission is about to commence.
It 'clears the net' by ensuring that all non-essential communication on the radio network is ceased, so that the critical targeting information can be transmitted without interference.
The warning order usually consists of the type of mission, the target description, the method of engagement, and the method of fire and control.