Knave is card (4)
I believe the answer is:
jack
I believe this is a double definition.
'knave' is the first definition.
('jack' can be a synonym of 'knave')
'is card' is the second definition.
(type of playing card)
(Other definitions for jack that I've seen before include "bowler rolls it" , "elevator?" , "Jill's other half?" , "Car lift" , "Knave; raising device" .)