Rubbish member of the Supremes (5)
I believe the answer is:
dross
'rubbish' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for dross that I've seen before include "Anything worthless" , "Lees" , "Slag!" , "Impurity" , "Scum on molten metals" .)