With a portion of fish, also duck, you have sherry (4)
I believe the answer is:
fino
'sherry' is the definition.
(I've seen this before)
'with a portion of fish also duck' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is found in the answer.
The remaining letters 'fin' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'you have' is the link.
Can you help me to learn more?
(Other definitions for fino that I've seen before include "Light dry sherry" , "Bone dry sherry, served chilled" , "Dry Spanish sherry" , "Light-coloured sherry" , "Driest of the sherries" .)