Operative (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">operative</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for agent that I've seen before include "Double-zero-seven, for example" , "He or she acts for actors" , "Substance that exerts some force or effect" , "One who acts for another" , "envoy" .)