Liver secretion (4)
I believe the answer is:
bile
'liver secretion' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bile that I've seen before include "Anger, bitterness" , "Peevish temper; a liver secretion" , "Digestive juice secreted by the liver" , "Irritability, bad temper" , "Bitter fluid from the liver" .)