Signal fires (7)
I believe the answer is:
beacons
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">signal fires</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 beacons that I've seen before include "Warning or guiding devices for ships" , "Signal fires" .)