You put your tea leaves into a small bag, stuff it inside the pig, then lowre the pig into a pot of hot water, let the tea 'brew' then remove the
pig and you have tea leaf free tea to drink.
There have been a couple of good guesses, but, I can't judge the size of the object without something like say a quarter lying next to it to compare
the size by. Any chance you could post a picture like that?
Edit* to add
I don't think it can be a tea holder, it looks like cast iron to me, iron and water don't mix well.