Overworked when bound to accept a raw beginner (5)
I believe the answer is:
tired
'overworked' is the definition.
(thesaurus)
'bound to accept a raw beginner' is the wordplay.
'bound' becomes 'tied' ('tie' can be a synonym of 'bind').
'to accept' is an insertion indicator.
'a raw beginner' becomes 'r' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tied' placed around 'r' is 'TIRED'.
'when' is the link.
Can you help me to learn more?
(Other definitions for tired that I've seen before include "Done in" , "Physically or mentally weary" , "Drowsy" , "Beat" , "getting bored" .)