Sourdough unit (4)
I believe the answer is:
loaf
'sourdough unit' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loaf that I've seen before include "Lounge about" , "To take things easy" , "Suffer loss of credibility" , "Be idle; something baked" , "Bread - brain!" .)