Two types of gold pen, the short one produces writing (6)
I believe the answer is:
author
'pen the short one produces writing' is the definition.
'author' can be an answer for 'pen' (authoring is a kind of penning). I'm not sure about the 'the short one produces writing' bit.
'two types of gold' is the wordplay.
'two types of' becomes 'auth' (I can't justify this - if you can you should believe this answer much more).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'auth'+'or'='AUTHOR'
Can you help me to learn more?
(Other definitions for author that I've seen before include "Someone who originates, causes or initiates something" , "Creator of written work" , "Generator, writer" , "One who has written" , "Literary creator" .)