The girl and I get on with the job (7)
I believe the answer is:
mission
'the job' is the definition.
(a mission is a job or task)
'the girl and i get on' is the wordplay.
'the girl' becomes 'miss' (term of address for an unmarried woman).
'and' is a charade indicator (letters next to each other).
'get' says to put letters next to each other.
'miss'+'i'+'on'='MISSION'
'with' is the link.
(Other definitions for mission that I've seen before include "religious establishment" , "In religious campaign" , "Ministry sent by a church to spread its teaching" , "important business" , "Important assignment" .)