Sister, in turn, ignoring the odds (3)
I believe the answer is:
nun
'sister' is the definition.
(thesaurus)
'in turn ignoring the odds' is the wordplay.
'ignoring the odds' indicates alternate letters (letters in odd-numbered positions are removed).
'in'+'turn'='inturn'
The alternating letters of 'inturn' are 'NUN'.
(Other definitions for nun that I've seen before include "Woman in Holy Orders" , "One who's taken vows" , "Woman in religious community" , "A palindromic holy woman" , "Sister of mercy" .)