If you serve in someone's stead, you're doing their job for them while they're not there. You probably intuitively know this word from the more common instead, which is just a shortening for "in the stead of." “can you go in my stead?”

What does in your stead mean?

Definition of in someone's/something's stead

formal. : in the place of someone or something She conducted the meeting in his stead.

Do you do in your stead?

As the representative of someone or something; in place of someone or something. (Typically used in slightly more formal language.) The boss isn't here at the moment, but I'd be happy to sign for the package in her stead. My horse was stolen, so I am forced to ride this donkey in its stead.