Walked up and down (5)
I believe the answer is:
paced
'walked up and down' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for paced that I've seen before include "Walked at a steady speed" , "Walked about in a preoccupied or frustrated way" , "Measured (a distance) by walking" , "Took steps" , "assist an athlete" .)