Give a false alarm (3,4)
I believe the answer is:
cry wolf
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">give a false alarm</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 cry wolf that I've seen before include "Cause a false alarm" , "alarm unnecessarily" , "Give unnecessary cause for alarm" , "Raise a false alarm too often, then not being believed when help is really needed" , "Give false alarm" .)