private; foot soldier; infantryman
Literal military rank: the lowest enlisted soldier. Used in historical or modern military contexts.
He enlisted as a private.
Even the role of a foot soldier is important on the battlefield.
underling; low-level worker; minor player
Figurative extension: a person of low rank or little influence in an organization, team, or group. Often used modestly or dismissively.
I'm still just a low-level worker in the company.
He contributed as a minor player on the team.