Halt progress after amber changes (7)
I believe the answer is:
embargo
'halt' is the definition.
(embargoing is a kind of halting)
'progress after amber changes' is the wordplay.
'progress' becomes 'go' (I've seen this in other clues).
'after' says to put letters next to each other.
'changes' is an anagram indicator.
'amber' with letters rearranged gives 'embar'.
'go' put after 'embar' is 'EMBARGO'.
(Other definitions for embargo that I've seen before include "Commercial break" , "Trade sanction" , "Official prohibition as on trade" , "Trading restriction" , "Official order forbidding something" .)