Picked up old draughtsman in US government department (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Sound-alike (picked up = heard) of EX (prefix ex- = previously but no longer = old) + CHECKER (a playing piece or “man” in the game of draughts, which is called checkers in the US). Old name for the government finance department now known as the Treasury; its boss is still known as the Chancellor of the Exchequer.