Take action on some issue (3)
I believe the answer is:
sue
This clue might be a double definition.
'take action' is the first definition.
(as in suing somebody in court)
'some issue' is the second definition.
The answer and definition can be both to do with social activities as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'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)" .)