Story in three parts (7)
I believe the answer is:
trilogy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">story in three parts</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 trilogy that I've seen before include "Group of three linked works" , "Group of three related works" , "collected works" , "series" , "Work in three parts" .)