Dash back with German article for part-exchange (5-2)
I believe the answer is:
trade-in
'part-exchange' is the definition.
(I've seen this before)
'dash back with german article' is the wordplay.
'dash' becomes 'dart' (synonyms).
'back' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'german article' becomes 'ein' (German indefinite article).
'dart' reversed gives 'trad'.
'trad'+'ein'='TRADE-IN'
'for' acts as a link.
(Other definitions for trade-in that I've seen before include "I daren't (anag)" , "Article used in part payment for another" , "Article used in part-exchange" , "Older article used in part payment to retailer" , "Trained (anag.)" .)