Ignoring bishop, big number managed church in innocence (9)
I believe the answer is:
ignorance
'innocence' is the definition.
(thesaurus)
'ignoring bishop big number managed church' is the wordplay.
'ignoring' indicates named letters should be taken away.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'number' becomes 'no' (abbreviation for 'number').
'managed' becomes 'ran' (both can mean organised or was in charge of).
'church' becomes 'ce' (abbreviation for Church of England).
'big' with 'b' taken out is 'ig'.
'ig'+'no'+'ran'+'ce'='IGNORANCE'
'in' is the link.
(Other definitions for ignorance that I've seen before include "Bliss perhaps" , "Lack of knowledge" , "being uninformed" , "lack of awareness" , "State of unknowing" .)