Ring launderer (6)
I believe the answer is:
washer
I believe this is a double definition.
'ring' is the first definition.
(I've seen this before)
'launderer' is the second definition.
(thesaurus)
(Other definitions for washer that I've seen before include "keep things firm" , "Ring under a nut" , "Seal preventing leakage" , "Rendered sightless" , "Metal disc for hawser" .)