do the work of

act for alternate answer for back up be in place of change commute cover for deputize displace double for fill in fill in for fill one's position go as proxy relieve replace serve in one's stead spell stand for stand in stand in for sub supersede supplant supply swap swap places with switch take another's place take over

replace supplant swap

alternate change commute deputize displace proxy relieve spell sub supersede switch

act for answer for back up be in place of cover for double for fill in for fill one's position go as serve in one's stead stand for stand in (for) swap places with take another's place take over

continue keep