Starts to arrange ingredients, blending oil into sauce (5)
I believe the answer is:
aioli
'sauce' is the definition.
(aioli sauce is a kind of sauce)
'starts to arrange ingredients blending oil' is the wordplay.
'starts to' indicates taking the first letters.
'blending' is an anagram indicator (letters blended or mixed into a new form).
The first letters of 'arrange ingredients' is 'ai'.
'oil' with letters rearranged gives 'oli'.
'ai'+'oli'='AIOLI'
'into' acts as a link.
(Other definitions for aioli that I've seen before include "A lamb joint; driven clouds" , "garlic sauce" , "Garlic mayo" , "11 [SAUCE]" , "Dressing" .)