Walker returns to give summary (5)
I believe the answer is:
recap
'summary' is the definition.
(recap is a kind of summary)
'walker returns' is the wordplay.
'walker' becomes 'pacer' (I've seen this before).
'returns' says the letters should be written in reverse.
'pacer' in reverse letter order is 'RECAP'.
'to give' acts as a link.
(Other definitions for recap that I've seen before include "Review" , "In brief, say it again" , "sum everything up" , "Go over again; summarise" , "Quickly run through" .)