Early leaver (3)
I believe the answer is:
rat
'early leaver?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
This is the entire clue.
Can you help me to learn more?
(Other definitions for rat that I've seen before include "Rodent - deserter" , "Despicable person" , "Plague-carrying rodent" , "Destructive rodent" , "shopper" .)