Jack, deceitful man (5)
I believe the answer is:
knave
This clue is a double definition.
'jack' is the first definition.
('knave' can be a synonym of 'jack')
'deceitful man' is the second definition.
(Other definitions for knave that I've seen before include "Yet he may be a diamond" , "Scoundrel - card" , "Jack - rotter" , "A rogue as in playing cards" , "Jack (card); base fellow" .)