Canary call (5)
I believe the answer is:
tweet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">canary call</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tweet that I've seen before include "Short message posted on the internet" , "Brief message" , "Online communication" , "Short message on a social medium" , "throwaway message?" .)