Scheming (3)
I believe the answer is:
sly
'scheming' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sly that I've seen before include "Devious and furtive" , "Unpleasantly cunning and secretive" , "Devious, cunning" , "Sneaky" , "'Cunning, wily (3)'" .)