Steel tower (5)
I believe the answer is:
pylon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">steel tower</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 pylon that I've seen before include "Electric cable tower" , "Power-cable support" , "Bearer of cable" , "Steel tower supporting high-tension wires" , "Grid cable support" .)