A nun cries out for protection (9)
I believe the answer is:
insurance
'for protection' is the definition.
(synonyms)
'a nun cries out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'a'+'nun'+'cries'='anuncries'
'anuncries' is an anagram of 'INSURANCE'.
(Other definitions for insurance that I've seen before include "Cover against mishaps" , "Promise of reimbursement in the case of loss" , "security" , "Cover against loss" , "Protection against a future eventuality" .)