Wily like ancient king, leader in Egypt (6)
I believe the answer is:
astute
'wily' is the definition.
(I've seen this before)
'like ancient king leader in egypt' is the wordplay.
'like' becomes 'as'.
'ancient king' becomes 'tut' (King Tut).
'leader in' says to take the initial letters.
The first letter of 'egypt' is 'e'.
'as'+'tut'+'e'='ASTUTE'
(Other definitions for astute that I've seen before include "Subtle" , "Perspicacious" , "Shrewd and sagacious" , "Wide" , "Sharp, shrewd" .)