Trader's first currency problems (7)
I believe the answer is:
trouble
'problems' is the definition.
(I've seen this before)
'trader's first currency' is the wordplay.
'first' indicates taking the first letters.
'currency' becomes 'rouble' (Russian rouble).
The initial letter of 'traders' is 't'.
't'+'rouble'='TROUBLE'
(Other definitions for trouble that I've seen before include "Distress - concern - effort" , "Misfortune" , "Worry - predicament" , "Disturb; unpleasantness" , "Hot water (if you are in it!)" .)