Using devious ways, wily Yanks capture head of evildoers (6)
I believe the answer is:
sneaky
But I can't explain it at all! Could you help me understand?
(Other definitions for sneaky that I've seen before include "Deceitful, underhand" , "Sly and devious" , "Cunning" , "Secretive and sly" , "Furtive, lacking candour" .)