The German paint finish -- it is giving you a skin complaint (10)
I believe the answer is:
dermatitis
'a skin complaint' is the definition.
(dermatitis is a skin condition)
'the german paint finish it is' is the wordplay.
'the german' becomes 'der' ('the' in German).
'paint finish' becomes 'mat' (a mat finish).
'der'+'mat'+'it'+'is'='DERMATITIS'
'giving you' is the link.
(Other definitions for dermatitis that I've seen before include "Met diarist (anag.)" , "Skin inflammation" , "Skin trouble" , "Skin ailment" .)