Monument to a doctor? (4)
I believe the answer is:
tomb
'monument' is the definition.
(I have seen 'Sepulchral monument ' mean 'tomb' so perhaps 'monument' could also mean 'tomb')
'to a doctor?' is the wordplay.
'a doctor?' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'to'+'mb'='TOMB'
(Other definitions for tomb that I've seen before include "Large vault" , "Burial-vault" , "Mausoleum" , "Place for the burial of a corpse" , "Burial site" .)