Graphite; leadwort (8)
I believe the answer is:
plumbago
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">graphite</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that graphite can be written as plumbago)</span><br/ ><br/ >'<span class="explanation-format__original">leadwort</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for plumbago that I've seen before include "Blue-flowered plant" , "Leadwort" , "climber in bed" , "Word for graphite" , "Evergreen shrub" .)