Extraordinary puzzle! Arsenic extracted from powdered magnesia? (6)
I believe the answer is:
enigma
'extraordinary puzzle arsenic' is the definition.
I know that 'puzzle' relates to this answer. I also know that both the answer and definition are singular nouns
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for enigma that I've seen before include "Conundrum" , "Puzzle of gamine (6)," , "Mysteriously puzzling person or thing" , "Puzzling person/thing" , "Mysterious or puzzling thing" .)