noun
skilled worker; craftsman; schemer
Refers to a person who is skilled at a particular job or trade, often with a nuance of being a go-getter or someone who gets things done. Can also imply a shrewd planner or schemer in certain contexts.
彼は腕のいい仕事師だ。
He is a skilled workman.
あの政治家は抜け目のない仕事師として知られている。
That politician is known as a shrewd schemer.
策士 explicitly means a strategist or schemer, often in political or military contexts, whereas 仕事師 carries this meaning only as a secondary, contextual nuance.
Compound of 仕事 (work, job) and 師 (master, specialist). The term likely developed from referring to a master of a trade to a more general term for a capable worker or schemer.