Disorderly flight when the tour is rearranged (4)
I believe the answer is:
rout
'disorderly flight' is the definition.
(I've seen this in another clue)
'the tour is rearranged' is the wordplay.
'is rearranged' indicates anagramming the letters.
'tour' with letters rearranged gives 'ROUT'.
'when' acts as a link.
(Other definitions for rout that I've seen before include "Inflict heavy defeat on" , "Devastating defeat" , "Whitewash" , "Put to flight, scatter" , "Utter defeat" .)