Fish or cobra cooked in beer (8)
I believe the answer is:
albacore
'fish' is the definition.
(albacore is a kind of fish)
'cobra cooked in beer' is the wordplay.
'cooked' indicates an anagram.
'in' means one lot of letters goes inside another.
'beer' becomes 'ale' (I've seen this before).
'cobra' is an anagram of 'bacor'.
'bacor' inserted inside 'ale' is 'ALBACORE'.
'or' is the link.
(Other definitions for albacore that I've seen before include "Long-fin tunny" , "Large tuna; able orca (anag.)" , "Variety of tuna" , "fish" .)