procurator

advocate counselor

attorney barrister counsel counsellor defender jurist mouthpiece pleader practitioner proctor solicitor

attorney-at-law jurisprudent legal adviser legal eagle legist member of the bar

backup replacement stand-in surrogate

agent alternate assistant auxiliary changeling delegate deputy double dummy equivalent expediency expedient fill in ghost locum makeshift proxy recourse refuge relay relief representative reserve resort resource standby stopgap sub succedaneum successor supplanter supply symbol temp temporary understudy vicar

dernier ressort ghost writer locum tenens pinch-hitter temporary expedient

being entity permanent