act for (?.)

• advance
• answer for
• appear for
• assist
• back up
• be instrumental
• change places with
• commission
• crowd out
• cut out
• deputize
• displace
• double for
• facilitate
• fill in for
• forward
• front for
• ghost
• ghostwrite
• go between
• mediate
• minister to
• pinch-hit
• pinch-hit for
• promote
• relieve
• replace
• represent
• serve
• speak for
• spell
• spell off
• stand in for
• subrogate
• subserve
• substitute for
• succeed
• supersede
• supplant
• swap places with
• understudy
• understudy for