Sum up business quickly for a Parisian citizen (9)
I believe the answer is:
muscovite
'a parisian citizen' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'sum up business quickly' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'business' becomes 'co' (short for company).
'quickly' becomes 'vite' (I can't justify this - if you can you should believe this answer much more).
'sum' backwards is 'mus'.
'mus'+'co'+'vite'='MUSCOVITE'
'for' is the link.
Can you help me to learn more?
(Other definitions for muscovite that I've seen before include "Russian" , "A citizen of Moscow" , "A native of Moscow" .)