Best place to start job on staff (4,8)
I believe the answer is:
pole position
'best place to start' is the definition.
(I've seen this before)
'job on staff' is the wordplay.
'job' becomes 'position' (position is a kind of job).
'on' is a charade indicator (letters next to each other).
'staff' becomes 'pole' (both can mean a stick).
'position' after 'pole' is 'POLE POSITION'.
(Other definitions for pole position that I've seen before include "Advantageous starting place" , "best place to start" , "Racers vie" , "at 90 degrees?" , "Good starting-point for race" .)