They're rigged (5)
I believe the answer is:
masts
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">they're rigged</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for masts that I've seen before include "things for flags" , "Eg, transmitter towers" .)