Take action on some issue (3)
I believe the answer is:
sue
This clue could be a double definition.
'take action' is the first definition.
(as in suing somebody in court)
'some issue' is the second definition.
The definition and answer can be both to do with social activities as well as being verbs in their base form.
Perhaps you can see an association between them that I can't see?
'on' is the link.
Can you help me to learn more?
(Other definitions for sue that I've seen before include "Bring a legal action" , "Susan (dim.)" , "Take legal action against (someone), girl's name" , "Begin legal proceedings against" , "Start proceedings against (someone)" .)