Timeline division (3)
I believe the answer is:
era
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">timeline division</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for era that I've seen before include "Specific time" , "A particular period of time" , "Period, age" , "Age of importance" , "Memorable period" .)