Liquid used in one's toilet (3)
I believe the answer is:
oil
'liquid' is the definition.
(I have seen 'Slippery liquid ' mean 'oil' so perhaps 'liquid' could also mean 'oil')
'in one's toilet' is the wordplay.
'in' says the answer is hidden in the clue.
'OIL' is hidden in the letters of 'ones toilet'.
'used' acts as a link.
(Other definitions for oil that I've seen before include "Fluid lubricant" , "Liquid gold" , "Lubricant or petroleum" , "Black gold" , "Anoint" .)