Unprepared former agency worker starts out running errands (2,7)

I believe the answer is:

ex tempore

'unprepared' is the definition.
(Latin term meaning improvised)

'former agency worker starts out running errands' is the wordplay.
'former' becomes 'ex'.
'agency worker' becomes 'temp'.
'starts' indicates taking the first letters.
The initial letters of 'out running errands' is 'ore'.
'ex'+'temp'+'ore'='EX TEMPORE'

I've seen this clue in The Guardian.

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