Perfect fish alla Livornese starters (5)
I believe the answer is:
ideal
'perfect' is the definition.
(similar in meaning)
'fish alla livornese starters' is the wordplay.
'fish' becomes 'ide' (type of fish).
'starters' says to take the initial letters (the letters which start the words).
The first letters of 'alla livornese' is 'al'.
'ide'+'al'='IDEAL'
(Other definitions for ideal that I've seen before include "superb specimen" , "immaculate" , "Dream" , "An - - Husband (Wilde)" , "existing only in imagination" .)