Guard

A guard is an individual assigned to watch over someone or something, or to protect someone.

Starfleet Officer Christopher Pike thought guard duty was incredibly boring as it required a person to stand in a single place for an extended period of time. 

Following the massacre on Tarsus IV Governor Gisela Ribeiro's former aide attempted to assassinate her with a grenade. This led the Starfleet team to believe there were still Security Force guards loyal to former Governor Kodos amongst the guards assigned to protect the Governor and her staff. They limited the individuals guarding prisoners such as Alexander Simmons to people they could absolutely trust, and supplemented them with security personnel from the USS Narbonne.