Invisible troublemaker
I believe the answer is:
gremlin
'invisible troublemaker' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gremlin that I've seen before include "Mischievous troublemaker" , "Mechanical mischief-maker" , "cause of trouble for airmen" , "Mischievous creature responsible for machine faults" , "Cause of unexpected mechanical problem" .)