The job is bungled twice in one day (7)
I believe the answer is:
mission
'the job' is the definition.
(a mission is a job or task)
'bungled twice in one day' is the wordplay.
'bungled twice' becomes 'issi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'one day' becomes 'mon' (abbreviation for Monday).
'issi' inserted into 'mon' is 'MISSION'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for mission that I've seen before include "Delegation" , "Important assignment" , "Assignment; expedition" , "Very dangerous assignment -- Tom Cruise film series" , "Journey with a specific purpose" .)