Sausage, unfinished slice and port, imbibing last of fizz (7)
I believe the answer is:
chorizo
'sausage' is the definition.
(type of sausage)
'unfinished slice and port imbibing last of fizz' is the wordplay.
'unfinished slice' becomes 'cho' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'port' becomes 'rio' (Rio de Janeiro is a port).
'imbibing' means one lot of letters goes inside another.
'last of' says to take the final letters.
The final letter of 'fizz' is 'z'.
'rio' enclosing 'z' is 'rizo'.
'cho'+'rizo'='CHORIZO'
Can you help me to learn more?
(Other definitions for chorizo that I've seen before include "Highly seasoned sausage" , "foreign meat" , "Spiced sausage" , "Spicy Spanish meat product" , "Spicy Spanish pork sausage" .)