Arrived and left train element (5)
I believe the answer is:
camel
'train element' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'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'
Can you help me to learn more?
(Other definitions for camel that I've seen before include "fawn" , "Humped mammal" , "Beastly type" , "Pale brown - animal" , "African transport" .)