Improbable story (4,4)
I believe the answer is:
tall tale
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">improbable story</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tall tale that I've seen before include "unbelievable" , "Improbable story" , "Fanciful story" , "Incredible story" , "Story that is difficult to believe, lofty narrative" .)