Tom has to dine on sauce (6)
I believe the answer is:
catsup
'sauce' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe there's an association between them I don't understand?
'tom has to dine' is the wordplay.
'tom' becomes 'cat' (I have seen 'A tom ' mean 'cat' so perhaps 'tom' could also mean 'cat').
'has' says to put letters next to each other.
'to dine' becomes 'sup' (synonyms).
'cat'+'sup'='CATSUP'
'on' acts as a link.
Can you help me to learn more?
(Other definitions for catsup that I've seen before include "Relish" , "something saucy from US" .)