Sentence:  Yet from the late thirteenth century the <WSD>metropolitan</WSD> based himself either in Moscow or Vladimir-on-the-Kliazma, which was also in Muscovite territory, and it became the ambition of the Muscovites to make this arrangement permanent. 
Meaning of the word marked with <WSD> tags:  A bishop empowered to oversee other bishops; an archbishop. (from 15th c.)