Sentence:  Here I must for the present break off my arduous work of educating the Press. We shall resume our studies later on; but just now I am tired of playing the <WSD>preceptor</WSD>; and the eager thirst of my pupils for improvement does not console me for the slowness of their progress. 
Meaning of the word marked with <WSD> tags:  A teacher or tutor, especially  a supervisor of new trainees.