Dead fish taken in to be cooked (8)
I believe the answer is:
obsolete
'dead' is the definition.
(similar in meaning)
'fish taken in to be cooked' is the wordplay.
'fish' becomes 'sole' (sole is a kind of fish).
'taken in' indicates putting letters inside.
'cooked' is an anagram indicator.
'to'+'be'='tobe'
'tobe' with letters rearranged gives 'obte'.
'sole' placed inside 'obte' is 'OBSOLETE'.
(Other definitions for obsolete that I've seen before include "Boots eel away, being out of date" , "Disused" , "Discontinued" , "No longer useful" , "Antiquated" .)