Girl in papers supporting soldiers heading off (4)
I believe the answer is:
enid
'girl' is the definition.
(girl's name)
'papers supporting soldiers heading off' is the wordplay.
'papers' becomes 'ID' (identification papers).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'soldiers' becomes 'men' (men can mean a group of soldiers).
'heading off' means to remove the first letter.
'men' with its initial letter removed is 'en'.
'id' put after 'en' is 'ENID'.
'in' acts as a link.
(Other definitions for enid that I've seen before include "Miss Blyton" , "'... Blyton, children's author (4)'" , "- Blyton, twentith century writer" , "- Blyton, children's writer" , "Dine with this girl" .)