Improves concerning documents (7)
I believe the answer is:
reforms
'improves' is the definition.
(reforming is a kind of improving)
'concerning documents' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'documents' becomes 'forms' (form is a kind of document).
're'+'forms'='REFORMS'
(Other definitions for reforms that I've seen before include "Changes for improvement" , "Makes changes" , "Mends ways, abandons badness" , "Adjustments" .)