Fable ending (5)
I believe the answer is:
moral
'fable ending' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for moral that I've seen before include "Relating to good and evil" , "Underlying significance of a story or event" , "ethical principle" , "knowing right from wrong" , "Relating to principles of right and wrong" .)