Dan Brown's first hit having shortage in stock (5,4)
I believe the answer is:
black belt
'hit having shortage in stock' is the definition.
I can't judge whether this definition defines the answer.
'dan brown's first' is the wordplay.
'dan' becomes 'belt' (I can't explain this - if you can you should believe this answer much more).
'brown' becomes 'black' (synonyms).
'first' means one lot of letters go next to another.
'belt' put after 'black' is 'BLACK BELT'.
Can you help me to learn more?
(Other definitions for black belt that I've seen before include "Proficient martial artist" , "Martial arts expert" , "Recognition of prowess in martial arts" , "Rank in the martial arts" , "Top level in judo" .)