They act for others (6)
I believe the answer is:
agents
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">they act for others</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 agents that I've seen before include "They do business on behalf of others" , "They operate on behalf of others" , "Instruments" , "They act for others" , "travelling salesmen" .)