Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "lǽre." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 601.
;adj. Empty [see next word.] [O. and N. lere house: R. Glouc. was þis lond of Romaynes almest lere, 81, 1: O. Sax. lári: O. H. Ger. lári inanis: Ger. leer.] v. ge-lǽr.