Synonyms and related words :
act for, answer for, appear for, back up, change places with, commission, crowd out, cut out, deputize, displace, double for, fill in for, front for, ghost, ghostwrite, pinch-hit, pinch-hit for, relieve, replace, represent, speak for, spell, spell off, subrogate, substitute for, succeed, supersede, supplant, swap places with, understudy, understudy for