Refuse to walk endlessly (4)
I believe the answer is:
marc
'refuse' is the definition.
(discarded material in winemaking)
'walk endlessly' is the wordplay.
'walk' becomes 'march' (marching is a kind of walking).
'endlessly' means to remove the last letter.
'march' with its final letter taken off is 'MARC'.
'to' acts as a link.
(Other definitions for marc that I've seen before include "Chagall for one" , "Spirit" , "A brandy; --- Chagall, artist" , "Type of eau-de-vie made from residue of grapes" , "Sort of brandy made from the remains of pressed grapes" .)