Preserve from doctor having bad meal outside (6)
I believe the answer is:
embalm
'preserve' is the definition.
(as in embalming a body)
'from doctor having bad meal outside' is the wordplay.
'from' becomes 'e' (I've seen this in other clues).
'doctor' becomes 'MB' (Bachelor of Medicine, Medicinae Baccalaureus).
'having' means one lot of letters go next to another.
'bad meal outside' becomes 'alm' (I can't justify this - if you can you should believe this answer much more).
'e'+'mb'+'alm'='EMBALM'
Can you help me to learn more?
(Other definitions for embalm that I've seen before include "Prepare corpse for preservation (6)" , "Treat corpse so as to retard decay" , "Preserve from decay in death with chemicals" , "Preserve corpse from decay" , "Treat corpse with preservatives" .)