Underhand — only Seth (anag) (2,3,3)
(Other definitions for on the sly that I've seen before include "With craft" , "in private" , "Honestly (anag) - dishonestly" , "Under the table" , "Done in an unpleasant and secret way" .)
(Other definitions for on the sly that I've seen before include "With craft" , "in private" , "Honestly (anag) - dishonestly" , "Under the table" , "Done in an unpleasant and secret way" .)