Delinquent, one that's sadly dropped out (8)
'delinquent' is the definition.
(both can mean a naughty child)
'one that's sadly dropped out' is the wordplay.
'one that's sadly dropped' becomes 'tear' (teardrops are released when someone is sad).
'out' becomes 'away' (synonyms).
(Other definitions for tearaway that I've seen before include "rebel", "reckless type", "A tough", "Reckless violent person", "Might I stir".)