Legal document; action (4)
I believe the answer is:
deed
I believe this is a double definition.
'legal document' is the first definition.
(deed is a kind of legal document)
'action' is the second definition.
(deed is a kind of action)
(Other definitions for deed that I've seen before include "Document showing ownership" , "Heroic exploit" , "documentary evidence" , "Intentional action" , "Something done" .)