Perfect oil stirred in garlic dip (5)
I believe the answer is:
aioli
'garlic dip' is the definition.
(I've seen this before)
'perfect oil stirred in' is the wordplay.
'perfect' becomes 'ai' (resembles A1, informal term meaning excellent).
'stirred' indicates anagramming the letters.
'in' indicates putting letters inside.
'oil' anagrammed gives 'iol'.
'ai' going around 'iol' is 'AIOLI'.
(Other definitions for aioli that I've seen before include "Garlic 9" , "Garnish" , "Garlic-flavoured mayonnaise" , "11 [SAUCE]" , "Garlic mayo" .)