Headword and gloss are both in the infinitive middle/passive form. The headword verb, ἀγείρω , is very rare in this form and is to be found in some versions of Homer, Iliad 10.127 (but not in Allen’s edition, which does not consider it genuine, and prefers ἠγερέθεσθαι : see web address 1). Nonetheless, note that the verse is quoted in this form by Eusthatius, Apollonius, the Etymologicum Gudianum and the Etymologicum Magnum.
This Homeric gloss seems to be taken from Lexicon Ambrosianum, because it is to be found (according to Adler) in Ambrosianus 12 Sup. 50, and we also have it (headword only) in Laurentianus 59.16 fol.187r. Note that it occurs in a Cyrillian gloss of Hesychius, Lexicon: eta59.