Cost of polish, not good (4)
I believe the answer is:
loss
'cost' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for loss that I've seen before include "Forgetting" , "One may be missed" , "Forfeiture" , "Destruction" , "Defeat (in sport)" .)