Royal Engineer (6)
I believe the answer is:
sapper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">royal engineer</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 sapper that I've seen before include "Something that wears down" , "Royal Engineer" , "Engineer private" , "Writer" , "Military miner" .)