Sentence:  According to Zimin, this individual was in the service of Prince Fedor Vasili'evich Riazanskii as early as 1498, two years after his service on the embassy to the <WSD>Crimea</WSD>. 
Meaning of the word marked with <WSD> tags:  The (Crimean Khanate), which for much of its history controlled most of the Crimean peninsula and various adjacent areas of the mainland.