Eg best for worst, verbally (7)
I believe the answer is:
synonym
'worst verbally' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for synonym that I've seen before include "Word with meaning similar to that of another" , "Word that can be exchanged for another" , "A word that is interchangeable with another" , "My sonny (anag)" , "Alternative word" .)