One who may discover her career’s ruined (10)
I believe the answer is:
researcher
'one who may discover' is the definition.
(someone who researches things)
'her career's ruined' is the wordplay.
'ruined' is an anagram indicator.
'her'+'careers'='hercareers'
'hercareers' with letters rearranged gives 'RESEARCHER'.
(Other definitions for researcher that I've seen before include "One making investigations" , "One investigating" , "One seeks information" , "analyst" , "Person investigating" .)