Heartless line ending great story (5)
I believe the answer is:
fable
'story' is the definition.
(I know that fable is a type of story)
'heartless line ending great' is the wordplay.
'heartless' means to remove the middle letters.
'ending' is a charade indicator (letters next to each other).
'great' becomes 'fab' (short for fabulous).
'line' with its middle taken out is 'le'.
'le' after 'fab' is 'FABLE'.
(Other definitions for fable that I've seen before include "there may be a moral to it" , "It's not true" , "Allegory" , "Story, often with moral" , "Aesop story" .)