Corrosive cleanser (3)
I believe the answer is:
lye
'corrosive cleanser' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lye that I've seen before include "Cleansing alkaline fluid" , "solution that comes out in the wash?" , "Alkali washing solution" , "Alkaline solution used for washing" , "Alkaline liquid" .)