Fish stew, a tin - wonderful (9)
I believe the answer is:
brilliant
'wonderful' is the definition.
(I know that wonderful can be written as brilliant)
'fish stew a tin' is the wordplay.
'fish' becomes 'brill' (brill is a kind of fish).
'stew' is an anagram indicator.
'a'+'tin'='atin'
'atin' is an anagram of 'iant'.
'brill'+'iant'='BRILLIANT'
(Other definitions for brilliant that I've seen before include "Magnificent" , "Very bright or vivid" , "Exceptionally clever" , "Brainy" , "Bright and sparkling" .)