Marches; army (6)
I believe the answer is:
troops
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">marches</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(trooping is a kind of marching)</span><br/ ><br/ >'<span class="explanation-format__original">army</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for troops that I've seen before include "Army" , "Military forces" , "men" , "Soldiers, armed forces" , "Cavalry" .)