Computer screen (3)
(Another definition for vdu that I've seen is " Visual display unit (abbrev.)".)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">computer screen</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that computer screen can be written as monitor)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for monitor that I've seen before include "Observe over time" , "Watch - lizard - warship - VDU" , "Keep an eye on" , "Vet" , "Keep a watching brief" .)