Former southern facility set up spear carriers? (6)
I believe the answer is:
extras
'spear carriers?' is the definition.
('extra' can be a synonym of 'spear carrier')
'former southern facility set up' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'southern' becomes 's' (abbreviation).
'facility' becomes 'art' (I've seen this in another clue).
'set up' shows that the letters should be reversed in order (in a down clue, letters go up).
's'+'art'='sart'
'sart' written backwards gives 'tras'.
'ex'+'tras'='EXTRAS'
(Other definitions for extras that I've seen before include "Runs not scored from the bat" , "Crowd scene actors" , "Wides, byes, etc." , "Sundries" , "walk-on parts" .)