Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "þeóstrian." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 729.
, þéstrian, þiéstrian, þístrian, þystrian; p. ode. I.to make dark or dim, to make the eye less capable of seeing, dim the sight :-- Se dæg bletit and ðióstraþ hiora eágan, Bt. 38, 5; Fox 206, 5. II.to grow dark or dim :-- His eágan þýstrodon caligaverunt oculi ejus, Gen. 27, 1: 48, 10. Ðýstrodan, Bd. 4, 10; S. 578, 19. Geseah ic onginnan ðýstrian ða stówe vidi obscurari incipere loca, 5, 12; S. 628, 10. Þa þestrede þe dai, Chr. 1135; Erl. 260, 32. Steorren sculen þeostren, O. E. Homl. i. 143, 20.