Department is related to organization as employee is related to:

Department is related to organization as employee is related to staff or personnel
An organization id composed of departments as staff/personnel is composed of employees. One good association to department : organization is the FAO or the Food and Agriculture Organization of the United States. FAO is composed of 6 departments. On the other hand, one good example for employee : staff/personnel is the government school employees. Employees comprises the teaching staff and the utilities or the job orders.

Department is the correct answer. This example describes a direct relationship. As an organization has many departements. And, a department has many employees. Therefore, A department is to an organization. In the same way, an employee is to the department.