Oil-drilling structures (4)
I believe the answer is:
rigs
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">oil-drilling structures</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 rigs that I've seen before include "Costumes; fraudulently manipulates (election)" , "Sets up (equipment)" , "Falsifies" , "Oil-drilling platforms" .)