Turned up a copper in standard old money (6)
I believe the answer is:
ducats
'old money' is the definition.
(historical type of gold coin)
'turned up a copper in standard' is the wordplay.
'turned up' shows that the letters should be reversed in order.
'copper' becomes 'Cu' (chemical symbol).
'in' means one lot of letters goes inside another.
'standard' becomes 'std' (abbreviation).
'a'+'cu'='acu'
'acu' placed into 'std' is 'stacud'.
'stacud' backwards is 'DUCATS'.
(Other definitions for ducats that I've seen before include "Old gold coins" , "pieces of old" , "money" , "Shylock lost" .)