Plodding (6)
I believe the answer is:
leaden
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plodding</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that plodding can be written as leaden)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for leaden that I've seen before include "Leaned over in slow, heavy way" , "Depressing - heavy" , "Heavy - overcast" , "Slow-moving, being like heavy metal" , "Heavy - plodding" .)