Monk after large pack animal (5)
I believe the answer is:
llama
'pack animal' is the definition.
(llamas are often used as pack animals)
'monk after large' is the wordplay.
'monk' becomes 'lama' (as in the Dalai Lama).
'after' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'lama' put after 'l' is 'LLAMA'.
(Other definitions for llama that I've seen before include "Camel-like wool source" , "Long-necked woolly animal" , "South American beast of burden" , "Peruvian transportation" , "South American transport animal" .)