Criminal's helper (9)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
accessory
'criminal's helper' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for accessory that I've seen before include "Hat or handbag, say" , "Criminal's helper" , "Useful added item" , "Item such as a handbag that goes with a dress" , "Confederate" .)