Ketchup base (6)
I believe the answer is:
tomato
'ketchup base' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tomato that I've seen before include "A motto turned out to be fruit or veg" , ""Plum" or "beef" fruit?" , "Type of sauce" , "It used to be call a love-apple" , "A motto, oddly, for this fruit" .)