Pretence included in realm of reformed criminal (10)
I believe the answer is:
malefactor
'criminal' is the definition.
(thesaurus)
'pretence included in realm of reformed' is the wordplay.
'pretence' becomes 'act'.
'included in' means one lot of letters goes inside another.
'reformed' is an anagram indicator.
'realm'+'of'='realmof'
'realmof' anagrammed gives 'malefor'.
'act' going within 'malefor' is 'MALEFACTOR'.
(Other definitions for malefactor that I've seen before include "One doing wrong" , "bad person?" , "Criminal, evil-doer" , "culprit?" , "Sinner" .)