Up past midnight with all the others (2,2)
I believe the answer is:
et al
'with all the others' is the definition.
(short for 'et alia', 'and others' in Latin)
'up past midnight' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'past midnight' becomes 'late' (late at night).
'late' in reverse letter order is 'ET AL'.
(Other definitions for et al that I've seen before include "and everyone else)" , "And the rest (Lat. abbr.)" , "... and other people (or things) (abbr)" , "'And others, to the old Romans (2,2)'" , "And others (abbrev.)" .)