Bouillabaisse base (5)
I believe the answer is:
broth
'bouillabaisse base' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for broth that I've seen before include "Bouillon" , "Setting for culture" , "that's good for an Irish boy" , "Type of soup" , "Soup made from water in which meat or fish has been boiled" .)