Many different parts initially for eminent nuclear physicist (7)

'physicist' is the definition.
(I know that Feynman has the occupation physicist)

'many different parts initially for eminent nuclear' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'parts' is an insertion indicator (in the sense of cuts or separates).
'initially' indicates taking the first letters.
The initial letters of 'for eminent nuclear' is 'fen'.
'many' anagrammed gives 'ynma'.
'ynma' going into 'fen' is 'FEYNMAN'.