Chap involved in scam, a colourful writer (6)
I believe the answer is:
crayon
'a colourful writer' is the definition.
'chap involved in scam' is the wordplay.
'chap' becomes 'ray' (**).
'involved in' means one lot of letters goes inside another.
'scam' becomes 'con' (I've seen this before).
'ray' put into 'con' is 'CRAYON'.
(Other definitions for crayon that I've seen before include "drawer" , "Wax colouring stick" , "Colouring pencil" , "Wax pen" , "Child's colouring stick" .)