Militant to work on arranged visit (8)
I believe the answer is:
activist
'militant' is the definition.
('activist' can be a synonym of 'militant')
'work on arranged visit' is the wordplay.
'work' becomes 'act' ('act' can be a synonym of 'work'**).
'on' indicates putting letters inside.
'arranged' is an anagram indicator.
'visit' anagrammed gives 'ivist'.
'act' put into 'ivist' is 'ACTIVIST'.
'to' is the link.
(Other definitions for activist that I've seen before include "Militant" , "forceful person" , "Vigorous political campaigner" , "One who plays a vigorous role, especially in politics" , "Human dynamo" .)