At back, chap, snake, one not worth listening to (8)
I believe the answer is:
prattler
'one not worth listening to' is the definition.
I can't judge whether this defines the answer.
'at back chap snake' is the wordplay.
'at' is a charade indicator (letters next to each other).
'back chap' becomes 'p' (I can't justify this - if you can you should give a lot more credence to this answer).
'snake' becomes 'rattler' (rattler is a kind of snake).
'p' next to 'rattler' is 'PRATTLER'.
Can you help me to learn more?
(Other definitions for prattler that I've seen before include "One talking foolishly" , "source of gossip" , "One may go on" , "One going on" , "One talks" .)