Second team player (4)
I believe the answer is:
back
I believe this clue is a double definition.
'second' is the first definition.
(to second a motion is to back it)
'team player' is the second definition.
(eg back is a type of rugby player)
(Other definitions for back that I've seen before include "Returned" , "Support - rear" , "Stern" , "ago" , "See 12" .)