Foam, suds (6)
I believe the answer is:
lather
This clue is a double definition.
'foam' is the first definition.
(I know that lather is a kind of foam)
'suds' is the second definition.
(lathering is a kind of sudsing)
(Other definitions for lather that I've seen before include "Froth formed by soap and liquid" , "Foamy soap as for shaving" , "stew" , "agitation" , "Foam made from soap" .)