Cook duck & hare for nobleman (8)
I believe the answer is:
archduke
'for nobleman' is the definition.
(I have seen 'Top nobleman' mean 'archduke' so perhaps 'nobleman' could also mean 'archduke')
'cook duck hare' is the wordplay.
'cook' indicates anagramming the letters.
'duck'+'hare'='duckhare'
'duckhare' with letters rearranged gives 'ARCHDUKE'.
(Other definitions for archduke that I've seen before include "European nobleman" , "Emperor's son" , "noted trio" , "European noble" , "Austrian noble" .)