Problem doesn't start with foreign currency (6)
I believe the answer is:
rouble
'foreign currency' is the definition.
(I've seen this in other clues)
'problem doesn't start' is the wordplay.
'problem' becomes 'trouble' (synonyms).
'doesn't start' means to remove the first letter.
'trouble' with its first letter removed is 'ROUBLE'.
'with' is the link.
(Other definitions for rouble that I've seen before include "Foreign money" , "ready in Belarus" , "Unit of money in Russia" , "Russian bread" , "Russian monetary unit" .)