The Suda here follows, but corrects, Photius pi1580 Theodoridis (who in turn follows Timaeus' Platonic Lexicon), where the headword is transmitted as purw/nwn.
The headword, as thus corrected, is the present participle (masculine nominative singular) of puro/w, from the root for 'fire' (cf. Chantraine, Dictionnaire étymologique s.v. pu=r, p. 922), either for placing something on the fire to cook or for placing something in a fire. It has evidently been extracted from somewhere; the possibilities are numerous. (There are none, as it happens, in Plato)