The headword is perfect, third person singular, of a(li/skomai. It must be quoted from somewhere -- perhaps Hyperides, Against Philippides 11; cf. eta 263.
It should have a passive sense, as translated here (and cf. eta 263). According to Adler the gloss in the Ambrosian Lexicon is e)krath/qh; and note also Hesychius eta404, glossing it with h(/tthtai.