Characteristic rush to return eastern currency no longer in use (9)
I believe the answer is:
trademark
'characteristic' is the definition.
(trademark is a kind of characteristic)
'rush to return eastern currency no longer in use' is the wordplay.
'rush' becomes 'dart' (darting is a kind of rushing**).
'to return' says the letters should be written backwards.
'eastern' becomes 'e'.
'currency no longer in use' becomes 'mark' (former German currency).
'dart' in reverse letter order is 'trad'.
'trad'+'e'+'mark'='TRADEMARK'
(Other definitions for trademark that I've seen before include "Distinguishing feature" , "Proprietary name" , "Registered sign of a manufacturer" , "Company's unique symbol" , "distinctive characteristic" .)