Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "cearc." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 119.
, es; m. n?Care, anxiety; cura, sollicitudo :-- Iudas ne meahte oncyrran cearces [MS. rex, =crex, =cerx, = cearx, = cearces] geníðlan Judas could not avert the pressure of anxiety, El. 610. v. carc.