Film preview (7)
I believe the answer is:
trailer
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">film preview</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for trailer that I've seen before include "advertise film" , "It's pulled by a vehicle" , "commercial vehicle drawn along" , "TV ad" , "one left behind" .)