Act up again (4)
I believe the answer is:
deed
'act' is the definition.
(I know that act can be written as deed)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for deed that I've seen before include "What's done" , "Heroic exploit" , "documentary evidence" , "Action - legal document" , "Something done" .)