Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "læst." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 602.
, e; f. A covering for the foot, a boot :-- Lǽste ocreæ, Ælfc. Gl. 29; Som. 61, 25; Wrt. Voc. 26, 24. v. lǽs-hosum, lǽst-wyrhta, lást, and Icel. leistr; m. a short sock: O. H. Ger. leist calopodium, forma: Ger. leisten.
act, performance(?) :-- Nalles hige gehyrdon háliges láre siððan leófes leóþ lǽste neár swég swiðrode they did not neglect the holy one's [Moses] teaching, after the loved one's lay, when the time drew nearer for action [crossing the Red Sea], and his voice died away, Cd. 158; Th. 197, 17: Exod. 308. v. Bouterwek's Cædmon i. 321; and cf. ful-lǽst, ge-lǽst.