Desert beast arrived last - first! (5)
'desert beast' is the definition.
'camel' can be an answer for 'beast' (I have seen 'Beast of burden' mean 'camel' so perhaps 'beast' could also mean 'camel'). I am unsure of the 'desert' bit.
'arrived last first' is the wordplay.
'arrived' becomes 'came' ('come' can be a synonym of 'arrive').
'last first' becomes 'l' (1st letter of 'last').
Can you help me to learn more?
(Other definitions for camel that I've seen before include "Humped creature", "Light yellowish-brown colour - ruminant", "Cud-chewing mammal of desert regions", "Pale brown - animal", "Humped beast".)