Assist in crime (4)
I believe the answer is:
abet
'assist in crime' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for abet that I've seen before include "Help in wrongdoing" , "Help to do something wrong" , "Criminally endorse" , "Encourage or assist (someone) to commit crime" , "helpful" .)