Hard graft never inspires a writer in the advertising industry (9)
I believe the answer is:
sloganeer
'writer in the advertising industry' is the definition.
The definition and answer can be both people as well as being singular nouns.
I also know that 'advertising' relates to this answer.
'hard graft never inspires a' is the wordplay.
'hard graft' becomes 'slog' (I can't explain this - if you can you should believe this answer much more).
'never' becomes 'ne'er' (synonyms).
'inspires' indicates putting letters inside (inspire means to breathe in).
'slog'+'neer'='slogneer'
'slogneer' enclosing 'a' is 'SLOGANEER'.
Can you help me to learn more?
(Other definitions for sloganeer that I've seen before include "bearer of a message" , "Use catchphrases" , "Inventor of memorable phrases for campaigning" , "sound bite producer?" .)