Share mistake and initially even Wall Street stalls? (8)
I believe the answer is:
parterre
'wall street stalls?' is the definition.
(term for theatre stalls in US - eg in Wall Street)
'share mistake and initially even' is the wordplay.
'share' becomes 'part' (synonyms).
'mistake' becomes 'err' (synonyms).
'and' means one lot of letters go next to another.
'initially even' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'part'+'err'+'e'='PARTERRE'
(Other definitions for parterre that I've seen before include "Part of the main floor of a theatre" , "The pit or bottom floor of a theatre" , "Theatre seating area on the ground floor" , "Flower-bed arrangement" , "Formally patterned flower garden" .)