Ace graduate redesigned store (7)
I believe the answer is:
maestro
'ace' is the definition.
(both can mean an expert or virtuoso)
'graduate redesigned store' is the wordplay.
'graduate' becomes 'ma' (abbreviation for Master of Arts).
'redesigned' indicates anagramming the letters.
'store' with letters rearranged gives 'estro'.
'ma'+'estro'='MAESTRO'
(Other definitions for maestro that I've seen before include "special performer" , "Eminent conductor or composer" , "Outstanding performer" , "Top music man" , "Good conductor" .)