The unglossed headword is masculine accusative singular or neuter nominative/accusative singular of the rare adjective ka/tauxmos (not in LSJ). Outside the Suda, its extant occurrences are in fact confined to Theophylact Simocatta (twice in the Histories, once in the Letters), so this headword is very probably quoted from Letter 8. (If so, it is neuter accusative, used as a substantive.)
[1] An approximation of Theophylact Simocatta, Histories 5.4.1 (using the dative singular of the headword).