The Webster's Dictionary of 1913 defined ‘catchup’ as: “table sauce made from mushrooms, tomatoes, walnuts, etc. [Also written as ketchup].”
This is in wiki under "ketchup" down the page
DM is not known for over subtlety in its clueing; the rest of te clue should confirm the veracity of the answer for you.
Happy new year to you and Chris!