Shellfish or half a long kipper? (6)
I believe the answer is:
winkle
'shellfish' is the definition.
(I know that winkle is a type of sea snail)
'half a long kipper?' is the wordplay.
'half a' suggests halving the letters.
'long kipper?' becomes 'ripvanwinkle' (I've seen this before).
'ripvanwinkle' with half the letters taken is 'WINKLE'.
'or' is the link.
(Other definitions for winkle that I've seen before include "Edible shellfish" , "Small shellfish" , "Small mollusc" , "Spiral-shelled mollusc" , "Sea snail" .)