Fossilized resin (5)
I believe the answer is:
amber
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fossilized resin</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 amber that I've seen before include "first light" , "Light giving warning" , "The traffic-light between red and green" , "Fossil resin used in jewellery" , "gemstone" .)