Sally, kind, idle after vacation (6)
I believe the answer is:
sortie
'sally' is the definition.
(I know that sally can be written as sortie)
'kind idle after vacation' is the wordplay.
'kind' becomes 'sort' (synonyms).
'after vacation' suggests removing the centre (the inside letters must vacate).
'idle' with its centre taken out is 'ie'.
'sort'+'ie'='SORTIE'
(Other definitions for sortie that I've seen before include "Operational flight by a bomber or fighter" , "Sudden attack by besieged troops" , "Attack launched from place of siege" , "Breakout by besieged garrison" , "Military manoeuvre" .)