Busy time for travel (4,4)
I believe the answer is:
rush hour
'busy time for travel' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rush hour that I've seen before include "Traffic-snarl period" , "Weekday crush of people and cars" , "Time of day when traffic is busiest" , "Time of maximum traffic" , "'Time of most road traffic (4,4)'" .)