Master chef, initially, a Scot (3)
I believe the answer is:
mac
'a scot' is the definition.
(many Scottish surnames begin with Mac)
'master chef initially' is the wordplay.
'master' becomes 'ma'.
'initially' says to take the initial letters.
The first letter of 'chef' is 'c'.
'ma'+'c'='MAC'
(Other definitions for mac that I've seen before include "A Gaelic son, often in name" , "It may help you keep dry" , "Coat - computer" , "Overcoat" , "PC" .)