God is after gold pen (6)
I believe the answer is:
author
'pen' is the definition.
(I know that author is a more specific form of the action pen)
'god is after gold' is the wordplay.
'god' becomes 'thor' (Thor is an example).
'is after' means one lot of letters go next to another.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'thor' after 'au' is 'AUTHOR'.
(Other definitions for author that I've seen before include "Writer - initiator" , "Book producer" , "Writer of a book or play" , "Someone who originates, causes or initiates something" , "Writer of a book, article or document" .)