Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "fácne." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 196.
;def. se fácna; seó, ðæt fácne; adj. Deceitful, fraudulent, factious; subdŏlus, dŏlōsus, factiōsus :-- Fácna dŏlōsus, Cot. 85: factiōsus, 198. Gif hit fácne is if it be fraudulent, L. Ethb. 77; Th. i. 22, 2. Fácnum wordum with factious words, Cd. 214; Th. 268, 35; Sat. 65. v. fǽcne; adj.