Unmarried woman I took on for a job (7)
I believe the answer is:
mission
'for a job' is the definition.
(a mission is a job or task)
'unmarried woman i took on' is the wordplay.
'unmarried woman' becomes 'miss' (as opposed to Mrs).
'took' is a charade indicator (letters next to each other).
'miss'+'i'+'on'='MISSION'
(Other definitions for mission that I've seen before include "1996 Tom Cruise spy film -- extremely dangerous assignment" , "Vocation; embassy" , "Special assignment" , "Assignment - calling" , "religious establishment" .)