Publication is to take action (5)
I believe the answer is:
issue
'publication' is the definition.
(I know that publication can be written as issue)
'is to take action' is the wordplay.
'to take action' becomes 'sue' (sue can mean to take legal action in court).
'is'+'sue'='ISSUE'
(Other definitions for issue that I've seen before include "Send out or distribute for use" , "Question in dispute to be settled" , "Difficulty" , "Regular publication" , "Offspring or edition" .)