As was said in the wiki above, one of the meanings of "наряд" is "order for work". Sometimes it is used in industry. In army it can mean auxilary activities, such as cleaning, serving food, etc, on the basis of rotation queue. There is common disciplinary punishment "два/три наряда вне очереди", which means soldier will do extra turns immidiately. But also "наряд" means such regular activities as patroling territory in army/police and in this case it also can be for the police/army unit itself.