Appetiser butcher's cooked, with thanks (10)
I believe the answer is:
bruschetta
'appetiser' is the definition.
(toasted bread served as an appetiser)
'butcher's cooked with thanks' is the wordplay.
'cooked' indicates an anagram.
'with' says to put letters next to each other.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'butchers' with letters rearranged gives 'bruschet'.
'bruschet'+'ta'='BRUSCHETTA'
(Other definitions for bruschetta that I've seen before include "Italian bread, toasted and served with olive oil, tomatoes, herbs, garlic etc" , "Ciabatta with olive oil and tomatoes" , "Italian dish" , "Italian toast" .)