Type of lens (4)
I believe the answer is:
zoom
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">type of lens</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 zoom that I've seen before include "go very fast" , "Video communications system" , "cinematic technique?" , "Camera lens function; move quickly" , "Move or rise rapidly - type of lens" .)