Claret ruined by additive that's sweet (7)
I believe the answer is:
treacle
'sweet' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
I also know that 'sweet' relates to this answer.
'claret ruined by additive' is the wordplay.
I cannot quite see how this works, but
an anagram of 'claret' is 'treacl' which is located in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'that's' is the link.
Can you help me to learn more?
(Other definitions for treacle that I've seen before include "Syrup, molasses" , "Viscous liquid" , "Carroll's sisters had to live with" , "well described by Dormouse" , "Syrup-like substance" .)