Bung soldier up into position (6)
I believe the answer is:
spigot
'bung' is the definition.
(thesaurus)
'soldier up into position' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'into' is an insertion indicator.
'position' becomes 'spot' ('spot' can be a synonym of 'position'**).
'gi' in reverse letter order is 'ig'.
'ig' inserted within 'spot' is 'SPIGOT'.
(Other definitions for spigot that I've seen before include "Peg to control the flow of a tap" , "Plug for a cask's vent hole" , "Peg for a cask's vent" , "Small plug for cask" , "Peg to seal vent in cask" .)