Chopper for one gaining unauthorised access perhaps (6)
I believe the answer is:
hacker
'chopper' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for hacker that I've seen before include "who bypasses security measures?" , "one for the chop?" , "Modern word for person who breaks into computer data" , "one's riding for pleasure" , "Anyone breaking into a computer system" .)