The meaning of "creamer" in relation to coffee is coffee creamer, which can be a light type of cream added to coffee or a nondairy cream-like substance known as nondairy creamer.
With relation to tea, the term "creamer" may also refer to coffee creamer. However, more often than not, it refers to a type of teaware.
A tea creamer of this kind is a small vessel used for pouring milk into tea (or directly into teacups before the tea if you follow the "milk first" school of tea preparation). These pieces of crockery often look a bit like a gravy boat and are typically found in Chinaware tea sets and other English-style tea sets.