Gold transaction a severe test (6)
I believe the answer is:
ordeal
'a severe test' is the definition.
(I've seen this before)
'gold transaction' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'transaction' becomes 'deal' (deal is a kind of transaction).
'or'+'deal'='ORDEAL'
(Other definitions for ordeal that I've seen before include "Difficult and painful experience" , "Disturbing experience" , "Horrific experience" , "One may be difficult" , "very hard test" .)