Do the man in - a writer (6)
I believe the answer is:
crayon
'a writer' is the definition.
(I've seen this before)
'do the man in' is the wordplay.
'do' becomes 'con' (both can mean to defraud).
'the man' becomes 'ray' (Man Ray was a 20th-century artist).
'in' indicates putting letters inside.
'con' placed around 'ray' is 'CRAYON'.
(Other definitions for crayon that I've seen before include "Coloured wax pencil" , "drawer" , "One colours with this" , "Stick of coloured wax for drawing (6)" , "pencil (13) [FRENCH]" .)