Vast stretch of time (3)
I believe the answer is:
eon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vast stretch of time</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 eon that I've seen before include "Major division of geological time" , "Era" , "In time, long division" , "thousand million years" , "Huge time period" .)