Assist in a crime (4)
I believe the answer is:
abet
'assist in a 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 "Crookedly endorse" , "Aid and assist" , "support wrongdoing" , "Assist criminally" , "Help in wrongdoing" .)