Coal worker (5)
I believe the answer is:
miner
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">coal worker</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for miner that I've seen before include "Underground worker" , "Excavator" , "One sent down for work" , "Collier" , "One works underground" .)