Excellent mix after stir (5-4)
I believe the answer is:
first rate
'excellent' is the definition.
(I've seen this before)
'mix after stir' is the wordplay.
'mix' indicates anagramming the letters.
'after'+'stir'='afterstir'
'afterstir' anagrammed gives 'FIRST-RATE'.
(Other definitions for first rate that I've seen before include "Very good quality" , "Topping" , "Splendid" , "exceptional" , "ace" .)