Currently the only way to clear out a Team Server TM is to delete documents through the Client or delete the whole thing from the Admin console.
It would be useful to be able to schedule this to happen automatically, for example every X period of time (configurable) or after a project TextBase has been updated.
This is an important maintenance task that can lead to issues if not kept on top of since it will keep growing (Db entries) and could have an impact on performance. Team Server TMs are needed on every project to enable internal matching.