Villain in Cairo, guessing (5)
I believe the answer is:
rogue
'villain' is the definition.
(I know that rogue is a type of villain)
'in cairo guessing' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ROGUE' can be found hidden inside 'cairo guessing'.
(Other definitions for rogue that I've seen before include "Fraud" , "Rapscallion" , "Blackguard" , "Scally" , "Dishonest man" .)