In bleaching, a percolating liquid may do so (5)
I believe the answer is:
leach
'percolating liquid may do so' is the definition.
I can't judge whether this definition defines the answer.
'in bleaching a' is the wordplay.
'in' says the answer is hidden in the clue.
'LEACH' is hidden in the letters of 'bleaching a'.
Can you help me to learn more?
(Other definitions for leach that I've seen before include "Make liquid percolate through soil" , "Permeate or penetrate gradually" , "Filtrate" , "Percolate - be removed by percolating liquid" , "Drain away by percolation" .)