Rework (old material) (6)
I believe the answer is:
rehash
'rework old material' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rehash that I've seen before include "Use again, with few or no changes" , "new disposition" , "Put old material into new form without much change" , "Reworking of old material" , "Work over (used material)" .)