Lead from salt mine of Wieliczka possibly taken outside with excessive cleaning (4,3,6)
I believe the answer is:
spit and polish
'excessive cleaning' is the definition.
(mocking term for excessive cleanliness)
'lead from salt mine of wieliczka possibly taken outside with' is the wordplay.
'lead from salt mine' becomes 'spit' (I can't explain this - if you can you should give a lot more credence to this answer).
'of wieliczka possibly' becomes 'polish' (Wieliczka is a Polish town).
'taken outside' means one lot of letters goes inside another.
'with' becomes 'and'.
'spit'+'polish'='spitpolish'
'spitpolish' placed around 'and' is 'SPIT AND POLISH'.
Can you help me to learn more?
(Other definitions for spit and polish that I've seen before include "Punctilious attention to neatness" , "associated with old buffers?" , "Good clean activity" , "Cleaning of equipment to excess - ceremony and formality" , "Military attention to neatness" .)