Ending article uploaded into document (6)
I believe the answer is:
finale
'ending' is the definition.
(I know that finale is a type of ending)
'article uploaded into document' is the wordplay.
'article' becomes 'an' (indefinite article).
'uploaded' says the letters should be written backwards.
'into' indicates putting letters inside.
'document' becomes 'file' (a file is a formal document).
'an' in reverse letter order is 'na'.
'na' inserted within 'file' is 'FINALE'.
(Other definitions for finale that I've seen before include "In leaf (anag.)" , "Conclusion of a performance" , "When it's grand, it's the last scene" , "Denouement" , "Conclusion, end" .)