Two women forming a poisonous whole (10)
I believe the answer is:
belladonna
'whole' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for belladonna that I've seen before include "brought a sparkle to the eye" , "drug supplier" , "Drug made from deadly nightshade" , "plant" , "Could it poison" .)