Same entry in Timaeus' Platonic Lexicon, compiled at some time between the first and the fourth centuries CE. Similar one, later, in Photius, Lexicon delta520, though the glossing there is corrupted into tele/sas ti u(pe/rteron didaska/lou. (The Suda's didaska/lw| is not in ms T, Adler reports, and in G and I seems to start a new entry, but the text she prints is surely the correct one.)
For a discussion of the middle voice of dida/skw, see delta 857. The present headword is its aorist participle, in the masculine nominative singular. It is presumably quoted from somewhere; didaca/menos itself does not occur in the extant works of Plato, though see Republic 467E for didacame/nous and Menexenus 238B for didaca/menoi; alternatively (since Timaeus did not in fact confine himself to Plato), from another author.