Prepare for burial (6)
I believe the answer is:
'prepare for burial' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for embalm that I've seen before include "Make into mummy" , "Treat corpse so as to retard decay" , "Preserve from decay in death with chemicals" , "Treat corpse with preservatives" , "Preserve body, mummify" .)