Bathroom bar (4)
I believe the answer is:
soap
'bathroom bar' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for soap that I've seen before include "It has detergent properties" , "Washing aid" , "Cleaning substance - melodramatic TV or radio series" , "TV programme - sudsy bar" , "Popular TV programme (which cleans?)" .)