• in sy's stead, in the stead of sy, on behalf of sy, on sy's behalf
• in lieu of sg, instead of sg
• acting, alternate, assistant, deputy, lieutenant, proxy, stand-in, sub, supply, surrogate, vicar, vicarious
• to deputize, to replace, to substitute, to supersede, to understudy
• to arrange for a supply
• to act as deputy for sy, to act for sy, to do duty for sy, to stand in, to sub for sy, to substitute for sy, to supply for sy, to supply sy's place, to take over from sy