These front-line defences are backed up by armoured units in reserve.
前线防御有后备装甲部队的支援。
《柯林斯英汉双解大词典》
2
After de-layering in this way, a company may be left with just a top level of senior managers, front-line managers and employees with direct contact with the public.
通过这种方式减少层级后，公司可能只剩下最高层管理人员、一线管理人员和与公众直接接触的员工。
3
He now favors giving front-line workers more responsibility.