the.com/operative

means A person who does operational work, especially the kind involving surveillance, infiltration, or other deniable tasks — or, more plainly, just something 'in effect' or 'functioning.'

from From Latin 'operari,' meaning 'to work' or 'to labor,' the same root that gives us 'operate' and 'opera.' The adjective sense (something that is 'operative,' i.e. functioning) came first; the noun sense — a person who 'operates,' especially in espionage or detective work — developed later as a euphemistic job title. It let agencies describe spies and informants without quite saying 'spy,' giving the word its enduring air of bureaucratic discretion.