Scientist, foremost among best of historical researchers (4)
I believe the answer is:
bohr
'scientist' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for bohr that I've seen before include "Niels -, Danish Nobel physicist" , "Danish Nobel-winning physicist (father or son)" , "scientist" .)