Paris underground (5)
I believe the answer is:
metro
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">paris underground</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 metro that I've seen before include "Urban railway system" , "The underground railway system in Paris" , "Parisian underground railway" , "what moves many Parisians" , "Paris underground rail system" .)