Title for Walter Scott or Isaac Newton (3)
I believe the answer is:
sir
I believe this is a double definition.
'title for walter scott' is the first definition.
(I've seen this in another clue)
'isaac newton' is the second definition.
(synonyms)
(Other definitions for sir that I've seen before include "Gentleman's form of address" , "Polite form of address to a man" , "Honorary male title" , "Title of knight or baronet" , "... ___ John Major" .)