Lo-o-ong time
I believe the answer is:
eon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lo-o-ong time</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for eon that I've seen before include "Very long period (US and technical spelling)" , "Immense period" , "Long period of time" , "Huge time period" , "Prolonged period" .)