Old copper that's still used by cooks (6)
I believe the answer is:
peeler
This clue might be a double definition.
'old copper' is the first definition.
(I've seen this before)
'used by cooks' is the second definition.
'that's still' acts as a link.
This may not be right. Some or all of it may belong to one of the definitions.
(Other definitions for peeler that I've seen before include "Devious type" , "stripper" , "Kitchen gadget - old policeman" , "Potato skinner" , "Old London policeman" .)