Baddie in an arcade game (3)
I believe the answer is:
cad
'baddie' is the definition.
(I've seen this in other clues)
'in an arcade game' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CAD' is hidden within 'arcade game'.
(Other definitions for cad that I've seen before include "Bounder, scoundrel" , "designing software" , "Blackguard" , "Rogue" , "Stinker" .)