Physicist of the naughty nineties (8)
I believe the answer is:
einstein
'physicist' is the definition.
(Einstein is an example)
'the naughty nineties' is the wordplay.
'the naughty' indicates anagramming the letters.
'nineties' is an anagram of 'EINSTEIN'.
'of' is the link.
(Other definitions for einstein that I've seen before include "Albert -, relativity physicist" , "Famous scientist of the nineties" , "Great scientist, founded theory of relativity" , "Nineties (anag.)" , "renowned scientist" .)