Herb, duck and orange cooked (7)
I believe the answer is:
oregano
'herb' is the definition.
(oregano is a kind of herb)
'duck and orange cooked' is the wordplay.
'duck' becomes 'o'.
'and' is a charade indicator (letters next to each other).
'cooked' indicates an anagram.
'orange' is an anagram of 'regano'.
'o'+'regano'='OREGANO'
(Other definitions for oregano that I've seen before include "Aromatic culinary herb" , "Sweet-smelling herb" , "Dried marjoram" , "Herb used in cookery" , "Marjoram-like herb" .)