Priest heading off beast of burden (4)
I believe the answer is:
lama
'priest' is the definition.
(lama is a kind of priest)
'heading off beast of burden' is the wordplay.
'heading off' means to remove the first letter.
'beast of burden' becomes 'llama' (I've seen this before).
'llama' with its first letter taken off is 'LAMA'.
(Other definitions for lama that I've seen before include "A Tibetan Buddhist priest or monk" , "A Buddist monk in Tibet" , "Religious leader" , "Holy man in Tibet" , "Tibetan high priest" .)