The distance, say, a cart should be reversed (7)
I believe the answer is:
yardage
'the distance' is the definition.
(yardage is a kind of distance)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for yardage that I've seen before include "Length in units of three feet" , "measure" , "Distance in three-foot units" , "Quantity of fabric" , "Distance sometimes measured in paces" .)