Organized trip in historic French town left unfinished (4)
I believe the answer is:
tour
'organized trip' is the definition.
(trip around a certain location)
'historic french town left unfinished' is the wordplay.
'historic french town' becomes 'Tours' (French city).
'left unfinished' means to remove the last letter.
'tours' with its final letter taken off is 'TOUR'.
'in' is the link.
(Other definitions for tour that I've seen before include "Pastoral people of East Africa" , "Term of duty" , "Pleasure trip going from place to place" , "Travel around" , "Travel round" .)