Deliberate wrecker (8)
I believe the answer is:
saboteur
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deliberate wrecker</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 saboteur that I've seen before include "Oen who causes industrial damage for pay" , "One causes damage to subvert" , "One who deliberately subverts" , "Deliberate wrecker" , "Our beats (anag) - fifth columnist" .)