Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "nesan." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 649.
;p. næs ; pl. nǽson ; pp. nesen To be saved from, to escape from :-- Ðam ðe mid sceolon mereflód nesan those who are to be saved with you from the flood (the living creatures in the ark with Noah), Cd. Th. 81, 7; Gen. 1341. v. ge-nesan.