Wife remains clean (4)
I believe the answer is:
wash
'clean' is the definition.
(washing is a kind of cleaning)
'wife remains' is the wordplay.
'wife' becomes 'w'.
'remains' becomes 'ash' (I've seen this before).
'w'+'ash'='WASH'
(Other definitions for wash that I've seen before include "The ----, inlet of the North Sea" , "Bear investigation" , "Clean with water" , "put on thin coat" , "Brush with ink; launder" .)