After time, currency is in difficulty (7)
I believe the answer is:
trouble
'difficulty' is the definition.
(trouble can mean a difficult situation)
'after time currency' is the wordplay.
'after' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'currency' becomes 'rouble' (Russian rouble).
't'+'rouble' is 'TROUBLE'.
'is in' is the link.
(Other definitions for trouble that I've seen before include "Misfortune" , "Cause distress to; unrest" , "'Care, distress (7)'" , "Distress, upset or worry" , "Difficulty, care, worry" .)