Scientist of the naughty Nineties! (8)
I believe the answer is:
einstein
'scientist' is the definition.
(Einstein is an example)
'the naughty nineties' is the wordplay.
'the naughty' is an anagram indicator.
'nineties' anagrammed gives 'EINSTEIN'.
'of' acts as a link.
(Other definitions for einstein that I've seen before include "Great scientist, founded theory of relativity" , "Highly influential German physicist" , "German expert on relativity" , "Albert -, relativity physicist" , "Physicist who formulated theories of relativity" .)