Early number? (5)
I believe the answer is:
ether
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">early number?</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 ether that I've seen before include "Old anaesthetic -- three (anag)" , "There goes the anaesthetic" , "It could knock you out" , "The gas is there, oddly" , "Formerly an anaesthetic" .)