Work in soapsuds evenly (4)
I believe the answer is:
opus
'work' is the definition.
(I've seen this before)
'soapsuds evenly' is the wordplay.
'evenly' means one should take alternating letters (even-numbered letters only).
The alternate letters of 'soapsuds' are 'OPUS'.
'in' acts as a link.
(Other definitions for opus that I've seen before include "Composition - magnum __" , "Work of 25 perhaps" , "Creative work, eg in writing, art or music" , "Piece of music (with number)" , "Composer's work" .)