Lasting a short time (5)
(Other definitions for brief that I've seen before include "description of Macbeth's candle" , "Terse" , "Summary of facts for barrister to consider" , "Provide someone with the facts of the case" , "Succinct" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lasting a short time</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 ephemeral that I've seen before include "A mere help (anag) - short-lived" , "Fugitive" , "Short-lived, passing quickly" , "short term gain" , "Transient, fleeting" .)