Educated dieter cooked with first utensil (7)
I believe the answer is:
erudite
'educated' is the definition.
(I've seen this before)
'dieter cooked with first utensil' is the wordplay.
'cooked with' indicates anagramming the letters (letters cooked into a new form).
'first utensil' becomes 'u' (1st letter of 'utensil').
'dieter' anagrammed with 'u' can make 'ERUDITE'.
(Other definitions for erudite that I've seen before include "Showing profound knowledge" , "Learned and literate" , "Learned and scholarly" , "Full of knowledge" , "Well educated, having great learning" .)