Stubborn so-and-so admits to last of drug running (9)
I believe the answer is:
dogmatist
'stubborn so-and-so' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'admits to last of drug running' is the wordplay.
'last of' says to take the final letters.
'running' is an anagram indicator (the letters run around to different places).
The final letter of 'drug' is 'g'.
'admits'+'to'+'g'='admitstog'
'admitstog' anagrammed gives 'DOGMATIST'.
Can you help me to learn more?
(Other definitions for dogmatist that I've seen before include "stickler" , "bigot" , "opinionated type" .)