Greek character behind banker and German dog (9)
I believe the answer is:
deerhound
'dog' is the definition.
(deerhound is a kind of dog)
'greek character behind banker and german' is the wordplay.
'greek character' becomes 'rho' (letter from the Greek alphabet).
'behind' is a charade indicator (letters next to each other).
'banker' becomes 'dee' (River Dee - something that banks).
'and german' becomes 'und' ('and' in German).
'rho' after 'dee' is 'deerho'.
'deerho'+'und'='DEERHOUND'
(Another definition for deerhound that I've seen is " Nude horde (anag) - dog".)