The price of iron ore eclipsing gold (3)
I believe the answer is:
fee
'the price' is the definition.
(price paid for a service)
'iron ore eclipsing gold' is the wordplay.
'iron' becomes 'fe' (Fe is the chemical symbol for iron).
'eclipsing' suggests deleting specific letters.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'ore' with 'or' taken away is 'e'.
'fe'+'e'='FEE'
'of' is the link.
(Other definitions for fee that I've seen before include "Cost" , "(Entry) charge" , "price" , "Sum payable to, say, barrister" , "Money paid for professional services" .)