Start shooting (4,4)
I believe the answer is:
open fire
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">start shooting</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 open fire that I've seen before include "One in grate; start shooting" , "traditional welcoming feature" , "Source of heat" , "Begin shooting" , "old-fashioned heater" .)