Scoff when the lustre has gone (6,3)
I believe the answer is:
polish off
'scoff' is the definition.
Although both the answer and definition are verbs in their base form, I don't see how one could define the other.
'the lustre has gone' is the wordplay.
'the lustre has' becomes 'polish' (I can't explain this - if you can you should give a lot more credence to this answer).
'gone' becomes 'off' (as in going off somewhere).
'polish'+'off'='POLISH OFF'
'when' acts as a link.
Can you help me to learn more?
(Other definitions for polish off that I've seen before include "Eat up" , "Finish completely - kill deliberately" , "Dispose of" , "Use varnish remover to get this" , "Consume (something) quickly" .)