Work the crowd, introducing Yankee investigator (4,4)
I believe the answer is:
moby dick
'work' is the definition.
(literary work)
'the crowd introducing yankee investigator' is the wordplay.
'the crowd' becomes 'mob' (mob is a kind of crowd).
'introducing' suggests taking the first letters.
'investigator' becomes 'dick' (dick can mean a detective).
The initial letter of 'yankee' is 'y'.
'mob'+'y'+'dick'='MOBY-DICK'
(Other definitions for moby dick that I've seen before include "Beast in book" , "Herman Melville's great novel of the White Whale" , "Book by Herman Melville" , "work by American" .)