Aunt mad for seafood (4)
I believe the answer is:
tuna
'seafood' is the definition.
(tuna is a kind of seafood)
'aunt mad' is the wordplay.
'mad' is an anagram indicator.
'aunt' anagrammed gives 'TUNA'.
'for' acts as a link.
(Other definitions for tuna that I've seen before include "Tunny" , "Large fish for the strange aunt" , "Large sea-fish" , "Common food fish" , "Large food fish" .)