A second prisoner departs, having stuffed sack and escaped (9)
I believe the answer is:
absconded
'escaped' is the definition.
(I've seen this before)
'a second prisoner departs having stuffed sack' is the wordplay.
'a second' becomes 's' (common abbreviation).
'prisoner' becomes 'con' (abbreviation for 'convict').
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'having stuffed' is an insertion indicator.
'sack' becomes 'abed' (I can't justify this - if you can you should believe this answer much more).
's'+'con'+'d'='scond'
'scond' put into 'abed' is 'ABSCONDED'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for absconded that I've seen before include "took French leave" , "Escaped" , "Ran away to avoid legal process" , "Left to avoid arrest" , "Fled to avoid arrest" .)