An animal arrived then left (5)
I believe the answer is:
camel
'an animal' is the definition.
(I know that Camel is a animal)
'arrived then left' is the wordplay.
'arrived' becomes 'came' (come can mean to appear or arrive).
'then' is a charade indicator (letters next to each other).
'left' becomes 'l' (common abbreviation).
'came'+'l'='CAMEL'
(Other definitions for camel that I've seen before include "fawn" , "Humped ungulate" , "Saharan carrier" , "Dromedary, perhaps" , "Humped creature" .)