Rebel base rout destroyed (8)
I believe the answer is:
saboteur
'rebel' is the definition.
(I've seen this before)
'base rout destroyed' is the wordplay.
'destroyed' is an anagram indicator.
'base'+'rout'='baserout'
'baserout' anagrammed gives 'SABOTEUR'.
(Other definitions for saboteur that I've seen before include "Vandal" , "One who deliberately subverts" , "Abort use (anag)" , "Hacker possibly" , "One deliberately damages" .)