Fish-and-chips sauce (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
tartar
'fish-and-chips sauce' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tartar that I've seen before include "A sauce to go with fish" , "plaque" , "saucy stuff" , "may be hard to brush off" , "Incrustation on teeth and gums" .)