Arrived and left on a pack animal (5)
I believe the answer is:
camel
'pack animal' is the definition.
'camel' can be an answer for 'animal' (I've seen this in other clues). I am not certain of the 'pack' bit.
'arrived and left' is the wordplay.
'arrived' becomes 'came' (come can mean to appear or arrive).
'and' says to put letters next to each other.
'left' becomes 'l' (common abbreviation).
'came'+'l'='CAMEL'
'on a' is the link.
Can you help me to learn more?
(Other definitions for camel that I've seen before include "Desert ruminant" , "Dromedary, perhaps" , "Humped ungulate" , "Light yellowish-brown colour - ruminant" , "A ship, some say" .)