Is it not prescribed by a general physician? (8)
I believe the answer is:
specific
'physician?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for specific that I've seen before include "Relating uniquely to a subject; precise, clear" , "Particular, exact" , "Definitive or exact" , "Particular, distinct" , "Explicit, definitive" .)