Soldier in the Royal Engineers (6)
I believe the answer is:
sapper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">soldier in the royal engineers</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 "Royal Engineer" , "Something that wears down" , "Soldier who digs trenches" , "Private in the British Royal Engineers" , "Engineer private" .)