Cyber criminal (6)
I believe the answer is:
hacker
'cyber criminal' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hacker that I've seen before include "Computer thief or axe wielder" , "Modern criminal who breaks into computers" , "Computer expert" , "Modern thief who breaks into computer systems" , "potentially a threat to security" .)