Aid's partner (4)
I believe the answer is:
abet
'aid's partner' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for abet that I've seen before include "helpful" , "Encourage (offence)" , "Assist in some nefarious activity" , "Assist (in wrongdoing)" , "support wrongdoing" .)