Injury in German wood (4)
I believe the answer is:
gash
'injury' is the definition.
(gash is a kind of injury)
'german wood' is the wordplay.
'german' becomes 'g' (abbreviation).
'wood' becomes 'ash' (wood from an ash tree).
'g'+'ash'='GASH'
'in' is the link.
(Other definitions for gash that I've seen before include "Long deep wound" , "Spare - rubbish" , "Deep open cut" , "Gaping wound" , "injury" .)