Novelist and ex-con back in custody for sport (7)
I believe the answer is:
archery
'for sport' is the definition.
(archery is a kind of sport)
'novelist and ex-con back in custody' is the wordplay.
I cannot really see how this works, but
'ex-con' could be 'archer' (I've seen this before) and 'archer' is found in the answer.
A single letter 'y' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for archery that I've seen before include "Bow and arrow sport" , "Arrow-shooting" , "The sport of bowmen" , "Bowmanship" , "The sport of shooting arrows with a bow" .)