
1) Best at artifice 2) Best at trickery 3) Foxiest 4) Fullest of tricks 5) Least aboveboard 6) Least candid 7) Least ingenuous 8) Least open 9) Least transparent 10) Maximally sharp 11) Maximally wily 12) Most arch 13) Most artful 14) Most clever 15) Most cunning 16) Most foxlike 17) Most foxy 18) Most insidious
Found on
https://www.crosswordclues.com/clue/slyest
No exact match found.