Rogue gets three keys (3)
I believe the answer is:
cad
'rogue' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cad that I've seen before include "designing software" , "Dishonourable man of decadent sort" , "Stinker" , "One behaves dishonourably" , "A knave, real rotter" .)