Wagon-lit (7)
I believe the answer is:
sleeper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wagon-lit</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sleeper that I've seen before include "Spy; part of railway" , "An overnight train?" , "Earring" , "Brace to support rail on track" , "Beam across railway track or berth on ship" .)