Unpleasant experience of gold trade (6)
I believe the answer is:
ordeal
'unpleasant experience' is the definition.
(I've seen this before)
'gold trade' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'trade' becomes 'deal' ('deal' can be a synonym of 'trade').
'or'+'deal'='ORDEAL'
'of' is the link.
(Other definitions for ordeal that I've seen before include "Loader (anag.)" , "Long painful experience" , "One may be difficult" , "Torment" , "Trial; nightmare" .)