Sentence:  But through the oligopoly, charcoal fuel proliferated throughout London's <WSD>trades</WSD> and industries.  By the 1200s, brewers and bakers, tilemakers, glassblowers, pottery producers, and a range of other craftsmen all became hour-to-hour consumers of charcoal. 
Meaning of the word marked with <WSD> tags:  Those who perform a particular kind of skilled work.