Tuna's prepared for family members (5)
I believe the answer is:
aunts
'family members' is the definition.
(I've seen this in another clue)
'tuna's prepared' is the wordplay.
'prepared' is an anagram indicator.
'tunas' anagrammed gives 'AUNTS'.
'for' acts as a link.
(Other definitions for aunts that I've seen before include "Relatives get a peculiar US tan" , "Relatives get bad US tan" , "Sally and others" , "Elderly female relations" , "Female relatives, usually older" .)