Turn pride into downfall (9)
I believe the answer is:
perdition
'downfall' is the definition.
(thesaurus)
'turn pride into' is the wordplay.
'turn' indicates an anagram.
'pride'+'into'='prideinto'
'prideinto' is an anagram of 'PERDITION'.
(Other definitions for perdition that I've seen before include "Eternal damnation" , "Irrevocable spiritual ruin" , "Everlasting punishment" .)