Where there's many a skill in trading (4)
I believe the answer is:
mart
'where' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'there's many a skill in trading' is the wordplay.
'there's' says to put letters next to each other.
'many' becomes 'M' (Roman numeral for a thousand).
'a skill in trading' becomes 'art' (I can't explain this - if you can you should give a lot more credence to this answer).
'm' next to 'art' is 'MART'.
Can you help me to learn more?
(Other definitions for mart that I've seen before include "US shop; market" , "Take tram to market" , "Place" , "Trading centre" .)