Falling stock market index pulled back (8)
I believe the answer is:
downward
'falling' is the definition.
(thesaurus)
'stock market index pulled back' is the wordplay.
'stock market index' becomes 'dow' (Dow Jones Industrial Average).
'pulled' becomes 'drawn' (drawing is a kind of pulling).
'back' is a reversal indicator.
'drawn' in reverse letter order is 'nward'.
'dow'+'nward'='DOWNWARD'
(Other definitions for downward that I've seen before include "To a lower place" , "for the worse?" , "Is off-peak travel heading" , "From higher to lower in direction" , "Declining" .)