He causes trouble in a washing machine perhaps (8)
I believe the answer is:
agitator
This clue might be a double definition.
'he causes trouble in a washing' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'machine perhaps' is the second definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
Can you help me to learn more?
(Other definitions for agitator that I've seen before include "A mover and shaker - or troublemaker" , "Subversive person" , "Demagogue" , "One causing trouble" , "A good mixer, maybe" .)