The headword is a deponent contract verb in the first person singular, present indicative middle/passive; see generally LSJ s.v. promna/omai. In such a form it might be simply paradigmatic, but in fact is taken to be quoted from its earliest attestation, at Plato, Theaetetus 151B (web address 1). There, speaking to Theaetetus, Socrates figuratively compares himself to a match-maker, redirecting less promising candidates for his own philosophical tutelage to the sophist Prodicus (pi 2365 and OCD(4) s.v.).
[1] The first gloss is the present indicative active, first person singular, of the contract verb procene/w, I am one's envoy, I protect, I recommend; cf. pi 2541, pi 2542, and see generally LSJ s.v. The second gloss is a later alternative form for promna/omai. The lemma is identically glossed in the Synagoge, Photius' Lexicon (pi1263 Theodoridis), and Lexica Segueriana 349.23; cf. Hesychius pi3584 s.v. promnw/menoi, courting for another, the present middle/passive participle of the headword verb in the masculine nominative (and vocative) plural.