Fault-causing sprite (7)
I believe the answer is:
gremlin
'fault-causing sprite' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for gremlin that I've seen before include "Fault-causing sprite" , "Troublemaking goblin" , "Mischievous machine saboteur" , "Trouble-making imp" , "Technical bug" .)