One striding over - go over again (5)
I believe the answer is:
recap
'go over again' is the definition.
(I've seen this in another clue)
'one striding over' is the wordplay.
'one striding' becomes 'pacer' (someone pacing around).
'over' says the letters should be written backwards.
'pacer' back-to-front is 'RECAP'.
(Other definitions for recap that I've seen before include "Final summary" , "Summarise at the end" , "Summary of main points" , "Go over again; summarise" , "Quickly run through" .)