Auxiliary spear carrier (5)
I believe the answer is:
extra
This clue is a double definition.
'auxiliary' is the first definition.
(thesaurus)
'spear carrier' is the second definition.
('extra' can be a synonym of 'spear carrier')
(Other definitions for extra that I've seen before include "Sundry" , "Accessory" , "particularly" , "fortuitous run" , "person in shot?" .)