accessory
US /əkˈses.ər.i/
UK /əkˈses.ər.i/

1.
a thing which can be added to something else in order to make it more useful, versatile, or attractive
:
•
She bought a new phone accessory.
•
Fashion accessories can complete an outfit.
2.
a person who helps in the commission of a crime but is not present at the scene
:
•
He was charged as an accessory to the crime.
•
The police are looking for an accessory after the fact.
1.
contributing to or aiding in a crime
:
•
He was found accessory to the murder.