The term 'WORKED AT (A TRADE)' can be summarized as having a job in a particular field or industry. The crossword solution for this term is 'PLIED', which means to practice or engage in a trade or profession. This could refer to any type of job, from a skilled trade such as carpentry or plumbing to a professional career such as accounting or law. It could also refer to a hobby or activity that someone does on a regular basis, such as playing an instrument or painting. In any case, it implies that the person has some level of expertise in the field they are working in.