Spy; functional (9)
I believe the answer is:
operative
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">spy</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">functional</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ ></span>
(Other definitions for operative that I've seen before include "Functioning; worker" , "secret agent" , "Machinist - working" , "Having force - skilled worker" , "Efficient" .)