Hard-to-believe story (4,4)
I believe the answer is:
tall tale
'hard-to-believe story' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tall tale that I've seen before include "Story that is difficult to believe, lofty narrative" , "unbelievable" , "Fanciful story" , "Improbable story" , "Incredible story" .)