Heavy-duty cleanser (3)
I believe the answer is:
lye
'heavy-duty 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 "Alkaline solution used for washing" , "caustic liquid" , "Alkali washing solution" , "Strongly alkaline solution for washing or cleansing" , "Solution obtained by leaching" .)