Wrote as American essayist, having moved gold to front, followed by diamonds (8)
I believe the answer is:
authored
'wrote' is the definition.
(to author something is to write it)
'gold to front followed by diamonds' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'front' indicates taking the first letters.
'followed by' becomes 'hore' (I can't explain this - if you can you should believe this answer much more).
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
The initial letter of 'to' is 't'.
'au'+'t'+'hore'+'d'='AUTHORED'
'as american essayist having moved' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for authored that I've seen before include "written" , "Wrote" .)