(n.) A subordinate; a subaltern.

U-boat U-boot Unterseeboot act for agent alternate alternative analogy backup change change places with changeling collateral common comparison copy counterfeit crowd out cut out demeaning dependent deputy disadvantaged displace double double for dummy equal equivalent ersatz exchange fake fill in for fill-in ghost ghostwrite ghostwriter humble imitation in the shade inferior infra dig junior less lesser locum tenens low lower lowly makeshift metaphor metonymy minor modest next best thing ordinary personnel phony pigboat pinch hitter pinch-hit proxy relief relieve replace replacement represent representative reserves ringer second rank second string secondary servile sign spares spell spell off stand in for stand-in subaltern subject submarine submersible subordinate subrogate subservient substituent substitute substitute for substitution succedaneum succeed supersede superseder supplant supplanter surrogate swap places with symbol synecdoche third rank third string token tributary under underprivileged understudy understudy for utility player vicar vice-president vice-regent vulgar