Soap unit (3)
I believe the answer is:
bar
'soap unit' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bar that I've seen before include "some chocolate" , "Drinks counter; restriction" , "whose moaning Tennyson hoped to prevent?" , "Lawyers may be called to it" , "Sandbank; drinking place" .)