Instigator captured in massacre at orphanage (7)
I believe the answer is:
creator
'instigator' is the definition.
(thesaurus)
'captured in massacre at orphanage' is the wordplay.
'captured in' indicates the answer is hidden within the clue.
'CREATOR' can be found hidden inside 'massacre at orphanage'.
(Other definitions for creator that I've seen before include "Person who makes or invents things" , "The Almighty" , "Inventor" , "Maker" , "Someone who makes something" .)