Some unfortunate fish ... (4)
I believe the answer is:
tuna
'fish' is the definition.
(tuna is a type of fish)
'some unfortunate' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'TUNA' is hidden in the letters of 'unfortunate'.
(Other definitions for tuna that I've seen before include "Large tasty fish, fond of a nut" , "Type of fish" , "(Meat of) large fish" , "Widely-eaten fish" , "Tunny" .)