Ring for a portion of fish and some sherry (4)
I believe the answer is:
fino
'some sherry' is the definition.
(I've seen this before)
'ring for a portion of fish' is the wordplay.
'ring' becomes 'O' (letter resembling a ring).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'a portion of fish' becomes 'fin' (fish have fins).
'o' put after 'fin' is 'FINO'.
'and' is the link.
(Other definitions for fino that I've seen before include "Bone dry sherry, served chilled" , "Dry Spanish sherry" , "Type of sherry" , "Driest of the sherries" , "Light-coloured sherry" .)