Speculator, one believing in hoarding gold (8)
I believe the answer is:
theorist
'speculator' is the definition.
(I've seen this before)
'one believing in hoarding gold' is the wordplay.
'one believing in' becomes 'theist' (I can't explain this - if you can you should give a lot more credence to this answer).
'hoarding' indicates putting letters inside.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'theist' enclosing 'or' is 'THEORIST'.
Can you help me to learn more?
(Other definitions for theorist that I've seen before include "An expert in abstract principles" , "Abstract reasoner" , "Speculator" , "Thinker" , "Expert in established hypotheses" .)