Signal for action (3)
I believe the answer is:
cue
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">signal for action</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 cue that I've seen before include "Signal (to actor)" , "Tapering stick used by snooker player" , "Signal for action" , "Potter" , "Sports implement" .)