No longer engaged to, is indifferent (8)
I believe the answer is:
detached
'indifferent' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for detached that I've seen before include "Clinical" , "Unconnected" , "free of ties" , "being sent on special assignment" , "Separate, disconnected" .)