Stop thinking underwear is being laundered? (9)
I believe the answer is:
brainwash
'stop thinking' is the definition.
(to brainwash someone is to stop them thinking)
'underwear is being laundered?' is the wordplay.
I cannot really understand how this works, but
'underwear' could be 'bra' (bra is a type of undergarment) and 'bra' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for brainwash that I've seen before include "Coerce into belief" , "Completely indoctrinate" , "Apply pressure" , "Subject someone to stressful indoctrination" , "clean mind?" .)