Deliberate wrecker (8)
I believe the answer is:
saboteur
'deliberate wrecker' is the definition.
(I've seen this before)
This is the entire clue.
(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" .)