(n.) A substitute or deputy; one filling an office for a time.

accepter acquirer artist-in-residence audience auditor beholder communicator consignee correspondent denizen dweller getter habitant hearer holder house detective incumbent inhabitant inhabiter inmate inpatient intern letter writer listener live-in maid locum tenens looker obtainer occupant occupier payee pen pal procurer receiver recipient residencer resident resident physician residentiary resider sojourner spectator taker tenant trustee viewer writer