Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dēfector, ōris, m. [deficio, no. I.], one who revolts from another; a revolter, rebel (post-Aug.): parata in defectores ultione, Tac. A. 1, 48; 12, 50 fin.; id. H. 3, 12; Suet. Ner. 43; Just. 16, 1, 13 al.: patris sui defectores, Tac. A. 11, 8.