Beer with a portion of duck and a vegetable (4)
I believe the answer is:
kale
'a vegetable' is the definition.
(kale is a kind of vegetable)
'beer with a portion of duck' is the wordplay.
'beer' becomes 'ale' (type of beer).
'with' is a charade indicator (letters next to each other).
'a portion of duck' becomes 'k' (I can't explain this - if you can you should give a lot more credence to this answer).
'ale' put after 'k' is 'KALE'.
'and' is the link.
Can you help me to learn more?
(Other definitions for kale that I've seen before include "Hardy cabbage" , "Vegetable" , "(Curly?) cabbage" , "Cabbage variety" , "Curly-leafed cabbage" .)