Wiktionary
first line manager
n. First-line managers of retail sales workers supervise the employees in the different specialty departments, such as produce, meat, and bakery. These managers train employees and schedule their hours; oversee ordering, inspection, pricing, and inventory of goods; monitor sales activity; and make reports to store managers.
Usage examples of "first line manager".
To the few who don't already know me, my name is Howard Farraday, and I'm the first line manager or senior engineer of the Kingsway telephone exchange.