Oven cleaner ingredient (3)
I believe the answer is:
lye
'oven cleaner ingredient' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lye that I've seen before include "solution that comes out in the wash?" , "Strong alkaline solution" , "Solution obtained by leaching" , "Strongly alkaline solution for washing or cleansing" , "Cleansing alkaline fluid" .)