A rake-off is a dishonest share of money taken from a deal — the cut someone quietly keeps when they should not. If a person helps a contract go through and then takes a slice of the profit in secret, that slice is a rake-off. It sits with words like kickback, but rake-off already says the share is dirty: it is not a normal, open commission. The word is informal, a little old-fashioned, and more at home in news about crime, sport, or shady business than in careful legal writing. Though actually, the picture behind it is someone raking money off the top, as you rake leaves off a path — taking a layer for themselves before the rest is shared.