Albacore or bluefin (4)
I believe the answer is:
tuna
I believe this clue is a double definition.
'albacore' is the first definition.
(I've seen this in another clue)
'bluefin' is the second definition.
(I've seen this in another clue)
(Other definitions for tuna that I've seen before include "Marine food for your strange aunt" , "Fish, often tinned" , "Large food fish" , "Large fish found in a nut" , "A fish; sounds like piano juster" .)