Soap lather (4)
I believe the answer is:
suds
'soap lather' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for suds that I've seen before include "Froth of soap and water" , "Mass of soap bubbles" , "Foam from detergent" , "Lather" , "Soap bubbles; scum" .)