Nouveau riche somewhat concerned with gold (5)
I believe the answer is:
auric
'concerned with gold' is the definition.
(auric means relating to gold)
'nouveau riche somewhat' is the wordplay.
'somewhat' indicates a hidden word.
'AURIC' is hidden in the letters of 'nouveau riche'.
(Other definitions for auric that I've seen before include "Pertaining to gold" , "French composer" , "- Goldfinger (Bond)" , "Hugh -, Labour party leader" , "Of or containing gold" .)