Preserve of English doctor, endless charity (6)
I believe the answer is:
embalm
'preserve' is the definition.
(embalming is a kind of preserving)
'english doctor endless charity' is the wordplay.
'english' becomes 'e' (abbreviation).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'endless' means to remove the last letter.
'charity' becomes 'alms' (alms is a kind of charity).
'alms' with its final letter removed is 'alm'.
'e'+'mb'+'alm'='EMBALM'
'of' is the link.
(Other definitions for embalm that I've seen before include "Prepare for burial" , "Preserve corpse from decay" , "Make into mummy" , "Use chemicals to preserve a dead body from decay" , "Treat corpse with preservatives" .)