Stop cooking, including European sauce (5)
I believe the answer is:
pesto
'sauce' is the definition.
(pesto is a type of sauce)
'stop cooking including european' is the wordplay.
'cooking' is an anagram indicator (letters cooked up into a new form).
'including' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'stop' with letters rearranged gives 'psto'.
'psto' enclosing 'e' is 'PESTO'.
(Other definitions for pesto that I've seen before include "Pasta sauce based on basil" , "Saucy work" , "Pasta sauce variety" , "Pasta sauce mainly of basil and cheese" , "sauce involving Basil" .)