Perfectionist maybe disposing of uranium to key operator (7)
I believe the answer is:
pianist
'key operator' is the definition.
(person who plays piano keys)
I can't explain the rest of the clue.
(Other definitions for pianist that I've seen before include "Expert on keys" , "Ashkenazy or Lang Lang" , "key man" , "One tickling the ivories" , "Person at keyboard" .)