What to call a baronet (3)
I believe the answer is:
sir
'what to call a baronet' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sir that I've seen before include "... ___ John Major" , "Title given to 10 Across" , "Gentleman's form of address" , "Title given to baronet" , "Honorary male title" .)